Hmm, that's kind of odd -- I can't reproduce this behavior, and the app is definitely set up to use the article language (instead of the user's language) for these messages. I recall this issue appearing in the past, and also recall fixing it 😅

Maybe the user was using an old version of the app?

That's a fair theory, however the diff suggests that the app used the proper App undo edit-tag, which was introduced pretty recently, and definitely after we fixed the article-language logic, iirc.
I suppose we could keep monitoring for any similar cases elsewhere.

https://quarry.wmcloud.org/query/85009 shows 95 app undos with non-English edit summaries in 2025, out of about 6000 total app undo. But the most recent one is today, so definitely still happening.

Still happening as of Dec 22, 2025. Updated query.