Usually it depends if I have anything to say or add. Sometimes it's just a quick comment but other times it's a longer post. It all depends on the thread and if I've already replied to it, and if so, if I have anything to address the new replies with.
most of the time, I have nothing to say on the subject. I'll read what people say, but if its something like "what's your favourite horror movie?" I wont reply because I don't like horror movies, but i'll read because I am interested.
I reply as much as people reply on my started threads. :lol:
I read a lot of threads. I don't necessarily reply to each. Sometimes I do want to say something like a one-liner comment. No matter how earnest that is, I'm afraid some people will find it a useless reply. In that case, I just rep the poster and put my comment on the rep box instead of posting it.