You read a long-ish piece. Naturally your brain makes an overall summary of it, rather than transcribing it word-for-word into your memory. Then instead of responding to the actual piece, you respond to the impression it left on your brain. So you make a lot of arguments that are addressed, possibly refuted, in the original post. You say, “Nuh uh! What about X!?”, when a simple re-reading of the original piece, or even a text search for “X,” would turn up a paragraph-long discussion of X. Or you say, “But what about Y?”, when the original piece hedges, “Of course, this argument does not apply to Y.”
I see so many comments like this. The criticisms in the comment are actually addressed in the original piece, but the commenter overlooked it. The antidote for this is to read the piece carefully, re-read your comment before posting, and delete the comment without posting if your point has already been adequately addressed. It’s a simple case where careful communication leads to better communication. I understand that we’re all busy, but if you can’t be bothered to read someone’s argument carefully, you shouldn’t be pounding out a reply to it. There is no merit to this kind of dialogue.
My longer list of bad comments is here. Possibly the one described in this post is a subspecies of one in the older post.