I like what Discourse does: it checks for similarity in your subject line (and can extend it to the body) and shows you a list of similar posts next to it. Whereas SO's unspoken motto that it lived and very much died by was always "gotcha": for askers, answerers, and moderators alike. Those meta-moderation traps were real, and it quickly got to where I just didn't bother doing it anymore. Selecting moderators by whether they agreed with the existing moderators was just another ingredient in the poisonous cocktail that SO mixed up itself and gulped down every day.