Griefing: If the system does not already, I think it should flag for review users who consistently downvote a particular user.
Cliques: Likewise if the same few people are consistently the first to upvote stories or comments of a particular user.
Multies/Sockpuppets: I think votes for a user buy another user from "too close" an ip address should be automatically discounted. I'm not sure how to define "too close" (and I suspect HN already does this)
Anonymous posting: I like the way MetaFilter handles anonymous posting instead of people making throwaway accounts. The downside of this is that 1) Posters have to really trust the site admins; 2) This becomes more work for the admins
Disallow noob posting articles: What % of the [DEAD] articles were posted by users with a very low karma? What % hit the front page?
(Yes, those last two are not directly related to the OP's comment but I feel they're ideas worth throwing out there)
I would be highly surprised if the majority of your suggestions are not already in HN, in some way except for the anonymous postings. As for the trust factor, that applies to MF just the same, unless you go out of your way to hide your traces you are always going to be identifiable to the site admins. Fortunately.
Disallowing noob posting articles would be a good thing, a very low karma cap on posting articles would help (5 or 10 or so).
That would be just enough to increase the cost of spam to the point where it would no longer be worth it.
The first thing I ever did with my HN account was make a submission that made it to the front page. There will be some false positives from banning noob submissions.
Cliques: Likewise if the same few people are consistently the first to upvote stories or comments of a particular user.
Multies/Sockpuppets: I think votes for a user buy another user from "too close" an ip address should be automatically discounted. I'm not sure how to define "too close" (and I suspect HN already does this)
Anonymous posting: I like the way MetaFilter handles anonymous posting instead of people making throwaway accounts. The downside of this is that 1) Posters have to really trust the site admins; 2) This becomes more work for the admins
Disallow noob posting articles: What % of the [DEAD] articles were posted by users with a very low karma? What % hit the front page?
(Yes, those last two are not directly related to the OP's comment but I feel they're ideas worth throwing out there)