diff --git a/lib/federation/activity_pub/activity_pub.ex b/lib/federation/activity_pub/activity_pub.ex
index 7dd39c604..a2852aa44 100644
--- a/lib/federation/activity_pub/activity_pub.ex
+++ b/lib/federation/activity_pub/activity_pub.ex
@@ -155,7 +155,7 @@ defmodule Mobilizon.Federation.ActivityPub do
   end
 
   # Create an activity from an event
-  @spec event_to_activity(%Event{}, boolean()) :: Activity.t()
+  @spec event_to_activity(Event.t(), boolean()) :: Activity.t()
   defp event_to_activity(%Event{} = event, local \\ true) do
     %Activity{
       recipients: [@public_ap_adress],
@@ -166,7 +166,7 @@ defmodule Mobilizon.Federation.ActivityPub do
   end
 
   # Create an activity from a comment
-  @spec comment_to_activity(%Comment{}, boolean()) :: Activity.t()
+  @spec comment_to_activity(Comment.t(), boolean()) :: Activity.t()
   defp comment_to_activity(%Comment{} = comment, local \\ true) do
     %Activity{
       recipients: [@public_ap_adress],
diff --git a/lib/federation/activity_pub/permission.ex b/lib/federation/activity_pub/permission.ex
index 309255282..7e78b317c 100644
--- a/lib/federation/activity_pub/permission.ex
+++ b/lib/federation/activity_pub/permission.ex
@@ -77,7 +77,7 @@ defmodule Mobilizon.Federation.ActivityPub.Permission do
 
   @spec can_manage_group_object?(
           existing_object_permissions(),
-          %Actor{url: String.t()},
+          Actor.t(),
           object()
         ) :: boolean()
   defp can_manage_group_object?(permission, %Actor{url: actor_url} = actor, object) do
diff --git a/lib/federation/activity_pub/transmogrifier.ex b/lib/federation/activity_pub/transmogrifier.ex
index df8ebf385..0d7f61e8b 100644
--- a/lib/federation/activity_pub/transmogrifier.ex
+++ b/lib/federation/activity_pub/transmogrifier.ex
@@ -967,10 +967,8 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
   defp do_handle_incoming_reject_invite(invite_object, %Actor{} = actor_rejecting) do
     with {:invite, {:ok, %Member{role: :invited, actor_id: actor_id} = member}} <-
            {:invite, get_member(invite_object)},
-         {:same_actor, true} <- {:same_actor, actor_rejecting.id == actor_id},
-         {:ok, activity, member} <-
-           Actions.Reject.reject(:invite, member, false) do
-      {:ok, activity, member}
+         {:same_actor, true} <- {:same_actor, actor_rejecting.id == actor_id} do
+      Actions.Reject.reject(:invite, member, false)
     end
   end
 
diff --git a/lib/federation/activity_pub/types/comments.ex b/lib/federation/activity_pub/types/comments.ex
index fbdd58a81..32ec11905 100644
--- a/lib/federation/activity_pub/types/comments.ex
+++ b/lib/federation/activity_pub/types/comments.ex
@@ -149,25 +149,23 @@ defmodule Mobilizon.Federation.ActivityPub.Types.Comments do
            ),
          tags <- ConverterUtils.fetch_tags(tags),
          mentions <- Map.get(args, :mentions, []) ++ ConverterUtils.fetch_mentions(mentions),
-         lang <- Map.get(args, :language, "und"),
-         args <-
-           Map.merge(args, %{
-             actor_id: Map.get(args, :actor_id),
-             text: text,
-             mentions: mentions,
-             tags: tags,
-             event: event,
-             in_reply_to_comment: in_reply_to_comment,
-             in_reply_to_comment_id:
-               if(is_nil(in_reply_to_comment), do: nil, else: Map.get(in_reply_to_comment, :id)),
-             origin_comment_id:
-               if(is_nil(in_reply_to_comment),
-                 do: nil,
-                 else: Comment.get_thread_id(in_reply_to_comment)
-               ),
-             language: if(lang == "und", do: LanguageDetection.detect(:comment, args), else: lang)
-           }) do
-      args
+         lang <- Map.get(args, :language, "und") do
+      Map.merge(args, %{
+        actor_id: Map.get(args, :actor_id),
+        text: text,
+        mentions: mentions,
+        tags: tags,
+        event: event,
+        in_reply_to_comment: in_reply_to_comment,
+        in_reply_to_comment_id:
+          if(is_nil(in_reply_to_comment), do: nil, else: Map.get(in_reply_to_comment, :id)),
+        origin_comment_id:
+          if(is_nil(in_reply_to_comment),
+            do: nil,
+            else: Comment.get_thread_id(in_reply_to_comment)
+          ),
+        language: if(lang == "und", do: LanguageDetection.detect(:comment, args), else: lang)
+      })
     end
   end
 
diff --git a/lib/federation/web_finger/web_finger.ex b/lib/federation/web_finger/web_finger.ex
index 7a952b436..9f1ae34ec 100644
--- a/lib/federation/web_finger/web_finger.ex
+++ b/lib/federation/web_finger/web_finger.ex
@@ -189,7 +189,7 @@ defmodule Mobilizon.Federation.WebFinger do
           {:ok, String.t()} | {:error, :link_not_found} | {:error, any()}
   defp find_webfinger_endpoint(domain) when is_binary(domain) do
     with {:ok, %Tesla.Env{status: 200, body: body}} <-
-           fetch_document("http://#{domain}/.well-known/host-meta"),
+           HostMetaClient.get("http://#{domain}/.well-known/host-meta"),
          link_template when is_binary(link_template) <- find_link_from_template(body) do
       {:ok, link_template}
     else
@@ -258,11 +258,6 @@ defmodule Mobilizon.Federation.WebFinger do
       {:error, :link_not_found}
   end
 
-  @spec fetch_document(String.t()) :: Tesla.Env.result()
-  defp fetch_document(endpoint) do
-    with {:error, err} <- HostMetaClient.get(endpoint), do: {:error, err}
-  end
-
   @spec address_invalid(String.t()) :: false | {:error, :invalid_address}
   defp address_invalid(address) do
     with %URI{host: host, scheme: scheme} <- URI.parse(address),
diff --git a/lib/federation/web_finger/xml_builder.ex b/lib/federation/web_finger/xml_builder.ex
index a45df0dde..9dd40af1c 100644
--- a/lib/federation/web_finger/xml_builder.ex
+++ b/lib/federation/web_finger/xml_builder.ex
@@ -39,9 +39,7 @@ defmodule Mobilizon.Federation.WebFinger.XmlBuilder do
   defp to_xml(content) when is_binary(content), do: to_string(content)
 
   defp to_xml(content) when is_list(content) do
-    content
-    |> Enum.map(&to_xml/1)
-    |> Enum.join()
+    Enum.map_join(content, &to_xml/1)
   end
 
   defp to_xml(%NaiveDateTime{} = time), do: NaiveDateTime.to_iso8601(time)
@@ -49,9 +47,7 @@ defmodule Mobilizon.Federation.WebFinger.XmlBuilder do
   @spec make_open_tag(tag :: atom, attributes :: map()) :: String.t()
   defp make_open_tag(tag, attributes) do
     attributes_string =
-      attributes
-      |> Enum.map(fn {attribute, value} -> "#{attribute}=\"#{value}\"" end)
-      |> Enum.join(" ")
+      Enum.map_join(attributes, " ", fn {attribute, value} -> "#{attribute}=\"#{value}\"" end)
 
     [to_string(tag), attributes_string] |> Enum.join(" ") |> String.trim()
   end
diff --git a/lib/graphql/api/utils.ex b/lib/graphql/api/utils.ex
index bde6ce86a..8318df97e 100644
--- a/lib/graphql/api/utils.ex
+++ b/lib/graphql/api/utils.ex
@@ -21,7 +21,7 @@ defmodule Mobilizon.GraphQL.API.Utils do
     text
     |> Formatter.html_escape("text/plain")
     |> Formatter.linkify(options)
-    |> (fn {text, mentions, tags} -> {String.replace(text, ~r/\r?\n/, "<br>"), mentions, tags} end).()
+    |> inject_new_lines()
   end
 
   def format_input(text, "text/html", options) do
@@ -30,6 +30,10 @@ defmodule Mobilizon.GraphQL.API.Utils do
     |> Formatter.linkify(options)
   end
 
+  defp inject_new_lines({text, mentions, tags}) do
+    {String.replace(text, ~r/\r?\n/, "<br>"), mentions, tags}
+  end
+
   @doc """
   Use the data-media-id attributes to extract media from body text
   """
diff --git a/lib/graphql/resolvers/media.ex b/lib/graphql/resolvers/media.ex
index 9a7ce5d3f..64f163e43 100644
--- a/lib/graphql/resolvers/media.ex
+++ b/lib/graphql/resolvers/media.ex
@@ -15,7 +15,7 @@ defmodule Mobilizon.GraphQL.Resolvers.Media do
   See Mobilizon.Web.Resolvers.Event.create_event/3
   """
   def media(%{picture_id: media_id} = _parent, _args, _resolution) do
-    with {:ok, media} <- do_fetch_media(media_id), do: {:ok, media}
+    do_fetch_media(media_id)
   end
 
   def media(%{picture: media} = _parent, _args, _resolution), do: {:ok, media}
diff --git a/lib/graphql/resolvers/user.ex b/lib/graphql/resolvers/user.ex
index afbd0909f..7e85a3e6e 100644
--- a/lib/graphql/resolvers/user.ex
+++ b/lib/graphql/resolvers/user.ex
@@ -559,11 +559,9 @@ defmodule Mobilizon.GraphQL.Resolvers.User do
            Enum.each(actors, fn actor ->
              actor_performing = Keyword.get(options, :actor_performing, actor)
              Actions.Delete.delete(actor, actor_performing, true)
-           end),
-         # Delete user
-         {:ok, user} <-
-           Users.delete_user(user, reserve_email: Keyword.get(options, :reserve_email, activated)) do
-      {:ok, user}
+           end) do
+      # Delete user
+      Users.delete_user(user, reserve_email: Keyword.get(options, :reserve_email, activated))
     end
   end
 
diff --git a/lib/mix/tasks/mobilizon/instance.ex b/lib/mix/tasks/mobilizon/instance.ex
index 0bbbd0c69..3d3dccc66 100644
--- a/lib/mix/tasks/mobilizon/instance.ex
+++ b/lib/mix/tasks/mobilizon/instance.ex
@@ -181,7 +181,7 @@ defmodule Mix.Tasks.Mobilizon.Instance do
     else
       shell_error(
         "The task would have overwritten the following files:\n" <>
-          (will_overwrite |> Enum.map(&"- #{&1}\n") |> Enum.join("")) <>
+          Enum.map_join(will_overwrite, "", &"- #{&1}\n") <>
           "Rerun with `-f/--force` to overwrite them."
       )
     end
diff --git a/lib/mix/tasks/mobilizon/users/show.ex b/lib/mix/tasks/mobilizon/users/show.ex
index c559f87f7..1b54eb96d 100644
--- a/lib/mix/tasks/mobilizon/users/show.ex
+++ b/lib/mix/tasks/mobilizon/users/show.ex
@@ -47,7 +47,7 @@ defmodule Mix.Tasks.Mobilizon.Users.Show do
   defp display_actors(actors) do
     """
     Identities (#{length(actors)}):
-    #{actors |> Enum.map(&display_actor/1) |> Enum.join("")}
+    #{Enum.map_join(actors, &display_actor/1)}
     """
   end
 
diff --git a/lib/service/address/address.ex b/lib/service/address/address.ex
index 59cc8682c..97392712b 100644
--- a/lib/service/address/address.ex
+++ b/lib/service/address/address.ex
@@ -57,8 +57,7 @@ defmodule Mobilizon.Service.Address do
       name: if(defined?(postal_code), do: "#{description} (#{postal_code})", else: description),
       alternative_name:
         [locality, country]
-        |> Enum.filter(& &1)
-        |> Enum.filter(&(&1 != description))
+        |> Enum.filter(&(&1 && &1 != description))
         |> Enum.join(", ")
     }
   end
diff --git a/lib/service/clean_orphan_media.ex b/lib/service/clean_orphan_media.ex
index 136815eb0..d8ab94dd3 100644
--- a/lib/service/clean_orphan_media.ex
+++ b/lib/service/clean_orphan_media.ex
@@ -46,10 +46,9 @@ defmodule Mobilizon.Service.CleanOrphanMedia do
                  [from: "posts_medias", param: "media_id"],
                  [from: "comments_medias", param: "media_id"]
                ]
-               |> Enum.map(fn [from: from, param: param] ->
+               |> Enum.map_join(" UNION ", fn [from: from, param: param] ->
                  "SELECT 1 FROM #{from} WHERE #{from}.#{param} = m0.id"
                end)
-               |> Enum.join(" UNION ")
                |> (&"NOT EXISTS(#{&1})").()
 
   @spec find_media(Keyword.t()) :: list(list(Media.t()))
diff --git a/lib/service/export/participants/csv.ex b/lib/service/export/participants/csv.ex
index b33fbb581..90aa737a6 100644
--- a/lib/service/export/participants/csv.ex
+++ b/lib/service/export/participants/csv.ex
@@ -41,7 +41,7 @@ defmodule Mobilizon.Service.Export.Participants.CSV do
                |> Repo.stream()
                |> Stream.map(&to_list/1)
                |> NimbleCSV.RFC4180.dump_to_iodata()
-               |> (fn stream -> Stream.concat([Enum.join(columns(), ","), "\n"], stream) end).()
+               |> add_header_column()
                |> Stream.each(fn line -> IO.write(file, line) end)
                |> Stream.run()
 
@@ -63,6 +63,10 @@ defmodule Mobilizon.Service.Export.Participants.CSV do
     end
   end
 
+  defp add_header_column(stream) do
+    Stream.concat([Enum.join(columns(), ","), "\n"], stream)
+  end
+
   @spec save_csv_upload(String.t(), String.t(), Event.t()) ::
           {:ok, Export.t()} | {:error, atom() | Ecto.Changeset.t()}
   defp save_csv_upload(full_path, filename, %Event{id: event_id, title: title}) do
diff --git a/lib/service/export/participants/ods.ex b/lib/service/export/participants/ods.ex
index ef73d25fe..679d418f2 100644
--- a/lib/service/export/participants/ods.ex
+++ b/lib/service/export/participants/ods.ex
@@ -39,7 +39,7 @@ defmodule Mobilizon.Service.Export.Participants.ODS do
                  |> Events.participant_for_event_export_query(Keyword.get(options, :roles, []))
                  |> Repo.all()
                  |> Enum.map(&to_list/1)
-                 |> (fn data -> Enum.concat([columns()], data) end).()
+                 |> add_header_columns()
                  |> generate_ods()
 
                File.write!(full_path, content)
@@ -62,6 +62,10 @@ defmodule Mobilizon.Service.Export.Participants.ODS do
     end
   end
 
+  defp add_header_columns(data) do
+    Enum.concat([columns()], data)
+  end
+
   defp generate_ods(data) do
     data
     |> Jason.encode!()
diff --git a/lib/service/formatter/formatter.ex b/lib/service/formatter/formatter.ex
index e30b1a996..32f515ffa 100644
--- a/lib/service/formatter/formatter.ex
+++ b/lib/service/formatter/formatter.ex
@@ -15,6 +15,8 @@ defmodule Mobilizon.Service.Formatter do
 
   alias Mobilizon.Web.Endpoint
 
+  # https://github.com/rrrene/credo/issues/912
+  # credo:disable-for-next-line Credo.Check.Readability.MaxLineLength
   @link_regex ~r"((?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~%:/?#[\]@!\$&'\(\)\*\+,;=.]+)|[0-9a-z+\-\.]+:[0-9a-z$-_.+!*'(),]+"ui
   @markdown_characters_regex ~r/(`|\*|_|{|}|[|]|\(|\)|#|\+|-|\.|!)/
 
diff --git a/lib/service/workers/build_search.ex b/lib/service/workers/build_search.ex
index fd94524e6..26b7fc7b4 100644
--- a/lib/service/workers/build_search.ex
+++ b/lib/service/workers/build_search.ex
@@ -56,8 +56,6 @@ defmodule Mobilizon.Service.Workers.BuildSearch do
   end
 
   defp get_tags_string(%Event{tags: tags}) do
-    tags
-    |> Enum.map(& &1.title)
-    |> Enum.join(" ")
+    Enum.map_join(tags, " ", & &1.title)
   end
 end
diff --git a/lib/service/workers/legacy_notifier_builder.ex b/lib/service/workers/legacy_notifier_builder.ex
index 8fe29e3ef..eed20f9ac 100644
--- a/lib/service/workers/legacy_notifier_builder.ex
+++ b/lib/service/workers/legacy_notifier_builder.ex
@@ -77,12 +77,16 @@ defmodule Mobilizon.Service.Workers.LegacyNotifierBuilder do
        ) do
     event_uuid
     |> Events.get_event_by_uuid_with_preload()
-    |> (fn %Event{organizer_actor: %Actor{id: actor_id}} -> [actor_id] end).()
+    |> organizer_actor_id()
     |> users_from_actor_ids(Keyword.fetch!(options, :author_id))
   end
 
   defp users_to_notify(_, _), do: []
 
+  defp organizer_actor_id(%Event{organizer_actor: %Actor{id: actor_id}}) do
+    [actor_id]
+  end
+
   @spec users_from_actor_ids(list(), integer() | String.t()) :: list(Users.t())
   defp users_from_actor_ids(actor_ids, author_id) do
     actor_ids
diff --git a/lib/web/proxy/reverse_proxy.ex b/lib/web/proxy/reverse_proxy.ex
index 9ac999386..79382f669 100644
--- a/lib/web/proxy/reverse_proxy.ex
+++ b/lib/web/proxy/reverse_proxy.ex
@@ -294,20 +294,22 @@ defmodule Mobilizon.Web.ReverseProxy do
     headers
     |> downcase_headers()
     |> Enum.filter(fn {k, _} -> k in @keep_req_headers end)
-    |> (fn headers ->
-          headers = headers ++ Keyword.get(opts, :req_headers, [])
+    |> maybe_keep_user_agent(opts)
+  end
 
-          if Keyword.get(opts, :keep_user_agent, false) do
-            List.keystore(
-              headers,
-              "user-agent",
-              0,
-              {"user-agent", Mobilizon.user_agent()}
-            )
-          else
-            headers
-          end
-        end).()
+  defp maybe_keep_user_agent(headers, opts) do
+    headers = headers ++ Keyword.get(opts, :req_headers, [])
+
+    if Keyword.get(opts, :keep_user_agent, false) do
+      List.keystore(
+        headers,
+        "user-agent",
+        0,
+        {"user-agent", Mobilizon.user_agent()}
+      )
+    else
+      headers
+    end
   end
 
   @spec build_resp_headers(list(tuple()), Keyword.t()) :: list(tuple())
@@ -316,7 +318,11 @@ defmodule Mobilizon.Web.ReverseProxy do
     |> Enum.filter(fn {k, _} -> k in @keep_resp_headers end)
     |> build_resp_cache_headers(opts)
     |> build_resp_content_disposition_header(opts)
-    |> (fn headers -> headers ++ Keyword.get(opts, :resp_headers, []) end).()
+    |> maybe_add_headers_from_opts(opts)
+  end
+
+  defp maybe_add_headers_from_opts(headers, opts) do
+    headers ++ Keyword.get(opts, :resp_headers, [])
   end
 
   @spec build_resp_cache_headers(list(tuple()), Keyword.t()) :: list(tuple())
diff --git a/test/service/export/icalendar_test.exs b/test/service/export/icalendar_test.exs
index 0cdadc93b..2d20e449e 100644
--- a/test/service/export/icalendar_test.exs
+++ b/test/service/export/icalendar_test.exs
@@ -19,7 +19,7 @@ defmodule Mobilizon.Service.ICalendarTest do
       VERSION:2.0
       PRODID:-//Elixir ICalendar//Mobilizon #{Mobilizon.Config.instance_version()}//EN
       BEGIN:VEVENT
-      CATEGORIES:#{event.tags |> Enum.map(& &1.title) |> Enum.join(",")}
+      CATEGORIES:#{Enum.map_join(event.tags, ",", & &1.title)}
       DESCRIPTION:Ceci est une description avec une première phrase assez longue\\,\\n      puis sur une seconde ligne
       DTEND:#{Value.to_ics(event.ends_on)}Z
       DTSTAMP:#{Value.to_ics(event.publish_at)}Z