This week we merged rEFLRfec4418313c4: Remove 'flaggedrevs-diffonly' message and related functionality. As a result, any localisation messages that were customized on-wiki and referred to this message now display a red link to "MediaWiki:Flaggedrevs-diffonly" instead.

User Kallichore reported this problem to me by email and linked https://de.wikipedia.org/wiki/Wikipedia:Fragen_zur_Wikipedia#MediaWiki:Flaggedrevs-diffonly.

Affected pages: https://global-search.toolforge.org/?q=flaggedrevs-diffonly&regex=1&namespaces=8&title= (16 results, but some were probably already fixed by users)

I was aware of this potential problem when making the change, but when I checked https://global-search.toolforge.org at the time, I got no results. I don't know if I used the wrong options or something, or if the tool was not working correctly.

The workaround is to remove {{MediaWiki:flaggedrevs-diffonly}} from the messages.

(Some wikis also worked around the problem by creating MediaWiki:flaggedrevs-diffonly: https://global-search.toolforge.org/?q=.&regex=1&namespaces=8&title=Flaggedrevs-diffonly but I suggest against that.)