I agree that it's a problem, one HN already has. I doubt we can solve it. We can maybe mitigate it, or at least not make it worse.
One tactic for not making it worse is to introduce changes slowly and with lots of time to assess the effect of each change. We're also willing to get procrustean, if we have to, about lopping off any changes that have bad effects. We've done that twice that I can think of.
Any new form of community moderation will come with a mechanism for overseeing it. For example, when we added vouching for users to rescue dead comments, we also added a review mechanism for moderators to catch vouching being abused—e.g. dead comments being rescued when they ought to stay dead because they violate the site guidelines. This combination, which was inspired by the flagging mechanism, turns out to work well. HN's userbase has vastly more capacity to sift through comments than moderators do, and makes good decisions most of the time. Meanwhile it's orders of magnitude less work for moderators to review vouches and flags than to read all the comments directly, and doing so lets us correct the community decisions that don't align with the site guidelines. Such an approach benefits from the strengths of both sides, users and moderators.
I joke that our goal is to turn HN into a pyramid scheme such that the community does all the work and we can just monitor things from time to time, but the real joke is that a 'pyramid scheme' in this case would amount to the holy grail of a self-regulating system. In my wildest dreams it would work à la the Tao Te Ching and simply run itself with the occasional tweak. But I don't expect to get off that easily.
The kind of community moderation we want has to do with protecting the values of the site—intellectual curiosity and civility—rather than particular content people post or views they hold. If you were to argue that those things can't completely be separated, I wouldn't disagree. But I do think we can influence it by how we design the software, and more importantly by how we clarify what the values of the site are. HN is getting to the point where we need a new round of specification about what the site is and what it is not. That's coming soon.