Well this isn't for in-game, but for on the forums.
I think it would be good if you could possibly like someones post? Sorta like Facebook, it's a very small idea and not much of a big change, it's something that I'd personally like.
If there was a topic that you were too busy to post on or don't know what to say, but you agree with whoever posted, it would be nice to have the possibility of liking, or even if there was a debate and you didn't want to get involved, but you agreed with them?
I don't know if its even possible to make on a forum.. *shrug*