Steps to reproduce:
- Go to Special:Watchlist in the mobile view (e.g. https://fa.m.wikipedia.org/wiki/Special:Watchlist?uselang=en)
- Click on the "diff" link for one of the changes
- It will take you to a URL similar to this one: https://fa.m.wikipedia.org/w/index.php?title=Special:MobileDiff/30145260&curid=5381367&uselang=en (note that both a curid and an oldid are present)
- What you see will *not* be a Diff page. It will be the "View" version of the page.
- Compare with https://fa.m.wikipedia.org/w/index.php?title=Special:MobileDiff/30145260&uselang=en with does not have a curid and what you get is an actual diff page.
Note that fawiki does not use the same "Watchlist" view in the mobile frontend as most other projects. We are part of some of the design programs (I bet @Ladsgroup can clarify which ones). Don't be surprised if https://fa.m.wikipedia.org/wiki/Special:Watchlist?uselang=en does not look like https://en.m.wikipedia.org/wiki/Special:Watchlist?uselang=en to you.
Note also that the RecentChanges page on mobile view is also broken in the same way.
Of note, the issue with curid confusing what should be rendered is coming up twice now (previously in T260713 where I assumed it was intended behavior, so I revised CheckUser code to simply not return curid when not applicable). Could we have possibly messed up the order in which parameters are consumed such that curid is now being checked before others? The issue reported here, with diff links, is certainly new.