Or a karmic penalty for upvoting a comment. That way you have to be respected by the community before you can upvote a thread. Maybe it would help curtail negative or snarky comments, if only because people upvoting have been around longer.

Stackexchange kind of does this. You need a certain (low) amount of karma before you can post certain types of submissions.

I think it's important to let new users have a visible voice, but giving older users greater powers for moderation might help preserve the older attitude of the site.