Well I’ll hop in to say that I prefer sites that allow ranking of comments, but I realize it is unlikely to be adopted here. I like being able to easily find posts that are considered insightful. Although I admit that a lot of times the ranking just flags posts that are considered funny.
I think the fears of gaming the rating system and group-think are a bit over-rated. While there would be a few posters that would try to abuse the system because they value the politics of the board over the content, I think they would be more than balanced by the level-headed posters, lurkers, and semi-lurkers that we have here – the quiet majority.
One option to consider is a rating system that only allows up-votes or likes (this is used in Google Reader for example). This allows users to flag posts that are good without providing an opportunity for petty down-vote wars. This particular system doesn’t address spam, but as has been stated earlier spam is already being managed.
An up-vote option gives feedback to the posters that ‘Hey, your post was useful.’ and it should even eliminate the dreaded single-word post ‘This’.
The only purpose of a karma system is e-peen. You also run into all kinds of problems with people trading ratings to boost their numbers, etc.
My cite: I used to moderate for a very large community (over 500k registered members) that used a karma system.
A karma system will do nothing to stop spammers. That’s what the “Report Post” button is for in the upper-right corner of every post on the board is for.
I like rep systems, but more because they’re fun rather than any benefit. Perhaps it’s because I rarely got negative reps, but seeing positive ones is always nice. They do add a little bit to forum control allowing people to speak out against those that are needlessly inflammatory, but not quite enough to run afoul of moderation; or are being glaringly dishonest.
I made a post a while back which is basically a copy/paste of the rules for rep from another board that used to use it (they stopped because they had to switch to different board software and most people miss it). I think the people that saw it abused had it implemented, but not regulated. From the boards that have ruleless rep I’ve been on, I agree, it sucks. But the rules in that post worked very well, and could be tailored to the culture of this board any way we wanted. The important bits are the concepts of “spreading rep around” (you can’t rep the same person until you rep 20 others first) and the rules violation of derepping someone just because you disagree or dislike them.
Overall I don’t particularly care that much, but I give at least one more vote to having one. Unfortunately it’s rather difficult to give concrete arguments in favor or against it without being directed to participate in a forum where it’s in place for a time, so I really have nothing too persuasive.
The karma system definitely has its uses, and its benefits, but I have no doubts that it would not work here. We’re too big, too conservative, and too general for it to be useful.