If the contributions of an editor are linked on a page, and that editor has contributions where the edit summary has been hidden by RevDel, Popups will show the diff anyway to administrators.

Narrative available at https://en.wikipedia.org/wiki/User_talk:MusikAnimal/Archive_32#RevDel.2Fpopups_bug

Example (you must be an en administrator to see it):

1. Go to above user talk page
2. Hover over 'contribs' in the user links for IP 78.127.222.52
3. If you are not an administrator, the edit summary in Popups will say 'Hidden revision', as it should
4. If you are an administrator, the edit summary is displayed in Popups