I don't think there's an obligation in a comment to address the parent of a post you are responding to, let alone all the parents which we'd get if that obligat

I don't think there's an obligation in a comment to address the parent of a post you are responding to, let alone all the parents which we'd get if that obligation was there and transitive :) You can also address only a part of the comment, like I did here. For instance, I have not given an opinion on the latter part of your comment.