An in-browser search from the top of the thread for “flagged” or “hidden” also does not find the those posts, because Discourse hasn’t sent that text from the browser. You have to painstakingly page through the thread page by page before an in-browser search works.
** For clarity, of course Discourse doesn’t know that this content was “maliciously hidden”, but (given the previous actions of some of the posters in that thread elsewhere in OSM) I suspect I know who flagged it and suspect that action would be perceived by most independent observers as malicious.
The use case here is the same as any other use case for find/search - being able to find things by searching for them.
That’s useful to moderators of course (“what did X say that caused their post to be hidden”) but until the bug where posts can be maliciously hidden is fixed it’s also useful to regular users too.