If someone wants to explain a down-vote, they'll say it in a reply to that comment. Requiring explanations will merely result in meaningless deluges of "not he

If someone wants to explain a down-vote, they'll say it in a reply to that comment. Requiring explanations will merely result in meaningless deluges of "not helpful", "bad", "this is a comment of a type I don't wish to see on HN", or people C&Ping long political rants.