I assume it's a manual decision, not strictly algorithmic. (Though it probably contains algorithmic elements, the final decision is done by a human.)
If true, then the inexorable outcome of this logic is that the front page isn't really controlled by the community, nor would we want it to be.
If not, then the details of the algorithm would be fascinating to learn about. It's not an easy problem to solve in general, and making a few dozen (hundred?) editorial decisions each day is probably more efficient, and more precise.
HN's system consists of community, software, and moderators, just as it always has. Moderation is a feedback module tacked on to try to prevent the system from landing in any of its default failure modes. That, alas, requires humans.