The “Clear Bookmarks” won’t ask for any confirmation whatsoever. It will just immediately clear all bookmarks in a topic, no matter how many of them there are or where there are (eg, whether they are currently loaded on the page or not).
While I haven’t experienced this problem myself, this looks like a trap for punishing people with fat fingers.
Also, why is this button the same as the “Bookmark” (topic / first post) button? They are definitely not opposites!
You’re again confusing the concept of a bookmarked topic with that of a bookmarked post, aren’t you?