Fix remote reports with comments revealing remote reporter (#17652)

* Display username rather than display name in report comment

For consistency with report notes and appeals

* Fix remote reports with comments revealing remote reporter

* Display instance name in placeholder

* Make instance name in report comment a link to the federation admin page

* Normalize i18n file

app/javascript/styles/mastodon/admin.scss

@@ -1367,18 +1367,22 @@ a.sparkline {
       line-height: 20px;
       margin-bottom: 4px;
 
-      .username a {
+      .username {
         color: $primary-text-color;
         font-weight: 500;
-        text-decoration: none;
         margin-right: 5px;
 
+        a {
+          color: inherit;
+          text-decoration: none;
+
           &:hover,
           &:focus,
           &:active {
             text-decoration: underline;
           }
         }
+      }
 
       time {
         margin-left: 5px;

app/views/admin/reports/show.html.haml

@@ -122,15 +122,28 @@
 = react_admin_component :report_reason_selector, id: @report.id, category: @report.category, rule_ids: @report.rule_ids&.map(&:to_s), disabled: @report.action_taken?
 
 - if @report.comment.present?
+  - if @report.account.instance_actor?
+    %p= t('admin.reports.comment_description_html', name: content_tag(:strong, site_hostname, class: 'username'))
+  - elsif @report.account.local?
     %p= t('admin.reports.comment_description_html', name: content_tag(:strong, @report.account.username, class: 'username'))
+  - else
+    %p= t('admin.reports.comment_description_html', name: t('admin.reports.remote_user_placeholder', instance: @report.account.domain))
 
   .report-notes
     .report-notes__item
+      - if @report.account.local? && !@report.account.instance_actor?
         = image_tag @report.account.avatar.url, class: 'report-notes__item__avatar'
+      - else
+        = image_tag(full_asset_url('avatars/original/missing.png', skip_pipeline: true), class: 'report-notes__item__avatar')
 
       .report-notes__item__header
         %span.username
-          = link_to display_name(@report.account), admin_account_path(@report.account_id)
+          - if @report.account.instance_actor?
+            = site_hostname
+          - elsif @report.account.local?
+            = link_to @report.account.username, admin_account_path(@report.account_id)
+          - else
+            = link_to @report.account.domain, admin_instance_path(@report.account.domain)
         %time{ datetime: @report.created_at.iso8601, title: l(@report.created_at) }
           - if @report.created_at.today?
             = t('admin.report_notes.today_at', time: l(@report.created_at, format: :time))

config/locales/en.yml

@@ -617,6 +617,7 @@ en:
         title: Notes
       notes_description_html: View and leave notes to other moderators and your future self
       quick_actions_description_html: 'Take a quick action or scroll down to see reported content:'
+      remote_user_placeholder: the remote user from %{instance}
       reopen: Reopen report
       report: 'Report #%{id}'
       reported_account: Reported account