Solutions:
1) Reddit staved off this effect for a while by both re-tuning the karma ranking computation, and wiping everyone's karma back to 0. The effect of hyper-people with too much power is problematic. I don't think that will work here, but it's possible a re-tune will help.
The general idea of a redo on the karma system was stated above: the right answer is to take a look at "good comments" and "bad comments" and look at new threads.
2) HN as invite only. Anyone can read, few can vote/comment. I'm not sure I'd make the cut if you were to have certain blessed voters/commenters. I like the suggested improvement of having this calculation be hidden, and never to show karma.
3) Moderators. The community I live in with the longest lifetime is "chowhound". They don't have a voting system (or good web technology), they have ruthless monitors. Monitors are never supposed to remove for quality of post, but they do simply nuke from orbit "that's what she said" post chains.
4) Look, there's one real fact here. As someone who, myself, sells a database product aimed at people like those who read HN, I have a huge incentive to get an article into HN. It could make or break my company - no fooling. Once you incent bright people to break your system, it will be broken. Socket puppet rings will rule. Eternal vigilance - that is, a moderator-like junta charged with looking at quality every few months and ruthlessly implementing whatever solution is correct at that time, is the only way to continue HN's spirit.
5) I will guarantee you that if something isn't done, there will simply be a slow, sure slide to mob rule and ignorance.