Is this at all related to T163061 or T175554? Or is this a content suppression feature which did exist at some point and now appears not to?

One more clue: Jimmy, another OSer at zhwiki, who is capable to suppress a FLOW topic. i.e. having such a button on his screen.

This is my screen ↓

@Wong128hk: Seeing https://zh.wikipedia.org/wiki/User:Wong128hk/common.js , does this still happen when using safemode? See https://www.mediawiki.org/wiki/Help:Locating_broken_scripts - thanks!

Can you provide the URL for that screenshot?

I'm able to see suppress button at https://zh.wikipedia.org/wiki/Topic:Wip4w0q8yyhrftwq under my staff account. since you also say another oversighter sees the button, I'd say this is a broken gadget/user script issue.

Could the OSer try to load the page in the safemode? They can do that by appending ?safemode=1 (or, if there's already ? in the URL, &safemode=1). For instance, for the URL I posted above, safemode version would be https://zh.wikipedia.org/wiki/Topic:Wip4w0q8yyhrftwq?safemode=1.

If it works in safemode, they'd need to disable (one by one) their gadgets and userscripts to see which one is broken. Once the problematic gadget/script is identified, the maintainers of that script should be alerted.

Hope this makes sense.

@sbassett @Reedy Hello, can you please advise if it's a good idea to publish this ticket now? AFAICS, it affects (affected?) a single user due to a broken gadget/user script rather than any issue in MW.

In T292919#7490122, @Urbanecm_WMF wrote:

@sbassett @Reedy Hello, can you please advise if it's a good idea to publish this ticket now? AFAICS, it affects (affected?) a single user due to a broken gadget/user script rather than any issue in MW.

It's fine to make this public now.