I don't want to just comment for the hell of it. Part of it is I that don't have that many strong opinions on things. I find a lot of the topics discussed interesting, but when it comes to having a say I don't feel that I have a strong enough connection to them to make a valid contribution.
Share what you find is interesting and say why you think it is. It's amazing how many fruitful conversations can come from even a small, offhand comment.