[jmillerinc]

I question whether SVD would yield good recommendations.

In any case, co-voting data is not scrape-able from the public HN site, so I think using keywords and urls is really the only realistic filtering option at this point.

[derefr]

You can use people's comments as a (loose) proxy for their interest in a post; people who comment on something are more likely to have upvoted it (or at least consider it worthwhile to talk about, even if they never really vote on things.) You could perhaps even use Sentiment analysis, and take negative (root-level) comments as downvotes (and prune any branch below a negative comment, because it's probably an argument.)