I understand. I do this a lot myself. I will read something very interesting and just digest it; I don't really have anything to add to the conversation. Other times, I may talk up a storm and comment several times. It depends a lot on mood too. Sometimes I feel like commenting and other times I just want to read.

It gets hadrer the bigger your flist gets. I enjoy knowing people from a variety of backgrounds and interests. I just don't always express it. :)