I posted a question here and I got an answer. I would like to reply to that answer. How do I do that? There is a comment button but it allows only a short reply. Mine is a little longer. Where is the Reply button?
You can submit comments to any answer to any of your own questions. Just press the "add comment" button. This is not a forum, so there's no reply button.
Try to avoid "thanks" comments and such. For that there's the "accept" (green) button and upvote. More information in the Help Center