It has happened to me more than once to be in a discussion and wanting to search some text within it using the browser's native search box. This becomes complicated when the discussion is long enough that it is loaded partially by the browser (e.g.: search for "love you" in https://discuss.flarum.org/d/20671-friendsofflarum-gamification/).
I guess a "search in this discussion" button could be added, but I would also be happy to have a button to "load full discussion" and then use the browser's native search. This second option would also simplify some use cases where you have to do a lot of scrolling on very long discussions and are bothered by the repeated slow downs due to the incremental loading. I appreciate that for very large discussions, loading all of it discussion can be very heavy on the browser, but I suspect that there is a wide range of usable discussion lengths before getting to that point.