I would really like to see this. I'm inclined say it shouldn't have any relation to karma or killing, because there's nothing inherently wrong with meta-discuss

I would really like to see this. I'm inclined say it shouldn't have any relation to karma or killing, because there's nothing inherently wrong with meta-discussion, but the front page would be infinitely more pleasant to me if I could see "100 comments (90 meta)", instead of guessing if there were really 100 things to say about the article or if after the only 10 someone just hit a nerve with a downvote or a pointless "this isn't HN" snark and started something big and ugly. I'd go so far as including a "meta" checkbox next to the reply button, defaulting to the parent's value, which it would be considered polite to set truthfully, but maybe that's just me.