Some threads topics I just don't want to see, usually the divisive ones that drone on and on in circular arguments, and it would be nice to simply have them disappear without ignoring the thread originator entirely.
I've seen it elsewhere, one site has a 90 day ignore feature which if the thread is still active requires a re-click to re-ignore. It worked well and kept the crap off my eyeballs, which I like.
If you use the "stop" following button to see your topics under »/forums/fav, all you have to do to ignore is to mark it "read" then never see it again or "unfollow" it.