It happens to all of us. It doesn't bother me as much the further I get in transition and I've come to realize why based on my own behavior on here. Sometimes I have nothing to add that hasn't already been said. Sometimes I have no idea what to say. Sometimes I have no experience with the topic, but I still find it interesting, so you'll see my name saying I'm reading it, but then get nothing from me. Sometimes the post may be during prime time for you, but I'm asleep or working. And yes, sometimes the posts are so long that I can't make it through the whole thing and don't want to comment based on half of the information. I'm guilty of the long posts myself. And sometimes, like this thread, I read it once and have no comment, then read it again after others comment and find I do have something to add.
I also only come here for about an hour a day, maybe. The same may be true of others. I was finding that the forums were getting me so excited about transitioning, that I would start moving faster than I should, so I limited my intake. There are hundreds of new posts across all forums daily here and I only hit the first 1-3 pages of new posts at the time I check, so if yours isn't recent to my check, I won't see it.