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 jokes, they'd just have to be asides to actual substance; D) encourage longer, better thought-out posts in general, and backing up of claims.