Cap the score that is displayed with a comment e.g., past 10 points, just display "10+". Don't display karma and average scores of users, again, past a certain point: this prevents (subconscious) game incentives which lead to e.g., posting comments that say something stupid or mean but which tend to agree with general tendencies of the site. For example, I can post a comment decrying Blub with a snide remark (e.g., "…
Actually, you just gave me a great idea (I think). The problem is mainly snide remarks, right? So make it impossible to make snide remakrs. How? Minimum comment length of ~50 words. This would A) get rid of casual snideyness, as those sorts of people wouldn't put in the effort to formulate a longer post; B) discourage crowd-pleasing one liners, which while enjoyable have a long term negative effect; C) still allow jo…
This would backfire because many useful comments aren't that long, and therefore people will be forced to pad them, this decreasing the s/n ratio.
For example, my paragraph above has 24 words.