Don't render the edit_form view for system notes

app/views/projects/notes/_note.html.haml

@@ -59,7 +59,9 @@
         .note-text
           = preserve do
             = markdown(note.note, {no_header_anchors: true})
-        = render 'projects/notes/edit_form', note: note
+        - unless note.system?
+          -# System notes can't be edited
+          = render 'projects/notes/edit_form', note: note
 
       - if note.attachment.url
         .note-attachment