“If I comment on blog posts, then I contribute to the intellectual content of the community, but this takes time and could be embarrassing.”
We have all heard that there is no such thing as a dumb question, and we have all heard a dumb question as well. If you feel you may have a dumb question, then just rephrase it. If your concerned about the “Deep sea fishing rights of teenagers?” you could ask, “What about teenagers?” and that may seem like a dumb question. I find that most dumb questions are really good questions, but suffer from poor abridgement. My advice is think about the context of your comment, but don’t give up on making the comment.