Do not persist translated system notes

app/services/system_note_service.rb

@@ -67,7 +67,7 @@ module SystemNoteService
     create_note(NoteSummary.new(noteable, project, author, body, action: 'assignee'))
   end
 
-  # Called when the assignees of an Issue is changed or removed
+  # Called when the assignees of an issuable is changed or removed
   #
   # issuable - Issuable object (responds to assignees)
   # project  - Project owning noteable
@@ -88,10 +88,12 @@ module SystemNoteService
   def change_issuable_assignees(issuable, project, author, old_assignees)
     unassigned_users = old_assignees - issuable.assignees
     added_users = issuable.assignees.to_a - old_assignees
-
     text_parts = []
+
+    Gitlab::I18n.with_default_locale do
       text_parts << "assigned to #{added_users.map(&:to_reference).to_sentence}" if added_users.any?
       text_parts << "unassigned #{unassigned_users.map(&:to_reference).to_sentence}" if unassigned_users.any?
+    end
 
     body = text_parts.join(' and ')
 

changelogs/unreleased/63262-notes-are-persisted-with-the-user-s-locale.yml

+---
+title: Do not translate system notes into author's language
+merge_request: 32264
+author:
+type: fixed

spec/services/system_note_service_spec.rb

@@ -212,6 +212,13 @@ describe SystemNoteService do
       expect(build_note([assignee, assignee1, assignee2], [assignee, assignee1])).to eq \
         "unassigned @#{assignee2.username}"
     end
+
+    it 'builds a correct phrase when the locale is different' do
+      Gitlab::I18n.with_locale('pt-BR') do
+        expect(build_note([assignee, assignee1, assignee2], [assignee3])).to eq \
+          "assigned to @#{assignee3.username} and unassigned @#{assignee.username}, @#{assignee1.username}, and @#{assignee2.username}"
+      end
+    end
   end
 
   describe '.change_milestone' do