Basically, he was too mean in a comment thread. The submissions on HN typically run media hot (X is doomed, Y is for idiots, Z is braindead) while the comments run media cold. He got the two mixed up, and was banned.
He called Sebastian Marshall "a prolix douchebag" in a comment, got hellbanned for it and promptly left when he realized it. That's pretty much the story. Evidently the hellban was lifted a little later (albeit not the ban on voting?), but he'd already gone by that point.
Edit: "for" -> "from"