I think the frontpage is great. That's probably because it's heavily moderated. I don't think there's a way to save the comments. Tragedy of the commons is inevitable when forums grow beyond a certain threshold. I 've even turned "showdead" to on as i 've found some great but controversial (read: thought-provoking) comments get completely buried under the usual HN popstars.

Might i suggest a crazy idea though: For every submission, ask 2 random members (who have a minimum but not high karma) to review it before it gets posted. If they disagree, ask a third. It's something i am testing out on my site, but i don't have sufficient user base.