My upvotes/downvotes are worth 2 points each and my supervotes are worth 6. A person with between 10 and 100 karma on the forum has an upvote worth 1 and a supervote worth 2 (the scaling system is described in this code here I think)
My concern is that this system lends itself to groupthink, whereby the dominant views or topics are liable to get more karma, giving holders of those views more voting power, giving users that makes posts they agree with or that they see as relevant more karma, etc.
Dissenting opinions or posts not of interest to the in-group are liable to be downvoted (although karma is meant to reflect quality or relevance of a post or comment, this is of course misused), which both hides those comments but also puts off dissenting voices from commenting/posting in the future.
The justification for the current system is that people with more karma are more likely to be have better understanding and judgement, less likely to be sockpuppets or trolls and so are better positioned to vote. This is a system ported over from LessWrong (described here).
Concerns about the scaling system have been discussed on the forum previously, for example here.
Is this system more beneficial than harmful?
Yes, I do post there. It's...fine. I don't exactly love it, but it at least doesn't give me an active feeling of disgust every time I use it (which the forum does).
This is unenforceable. In fact that whole section is unenforceable:
I agree that if everyone followed these norms there wouldn't be a problem, however they aren't, and there isn't a way to make them. Worse, the incentives work against a lot of these norms:
If someone is spreading opinions you disagree with, then the karma system makes strong-downvoting them an excellent way to hinder their ability to do so.
If your friend makes mediocre posts but he also upvotes all your mediocre posts, then upvoting them is a great way to ensure your posts get more exposure.
If an HBDer sees me sharing studies that undermine HBD, then a great way to lessen my ability to do so is downvote other posts and comments I've written (and downvote the posts and comments I write in the future too). Worst case scenario, my reach decreases. Best case scenario, I start to self-censor or leave the forum (aka what happened).
Voting is anonymous, so unless you "mass" vote it will remain undetected. It's good that they have written down these norms, but it'll barely do anything even if it was better known. The karma system simply works against it. It's not enough to say "pretty-please don't act on the bad incentives we've created", you have to actually give people good incentives.