The only reason I've ever liked a thread was to track threads that I have made, still waiting for a saved threads feature and the return of all of my old saved threads. It just never really crosses my mind to like any threads so I just don't do it, and when it does I think to myself, "Did I actually particularly like this thread? Or am I just thinking about liking it because I posted in it?" If I liked every thread I posted in my profile would get cluttered with them and it would kind of defeat the purpose of liking in the first place. I guess all of that was rather off topic, but liking an individual reply would make more sense to me because of what I just said because liking a reply is far more specific than liking an entire thread.