I would have a check box next to the add comment button that says "this is a nice comment" and if someone posts without ticking that box, redirect them to a pag

I would have a check box next to the add comment button that says "this is a nice comment" and if someone posts without ticking that box, redirect them to a page on civility. If nothing else it'd be interesting to see if people tick it and still comment mean spirited things, this way they actually have to acknowledge they are flying in the face of Hacker News every time they comment.