I do think we'd benefit from more guidance, but 'pg is pretty hands-off on this stuff. Graham could say today "no Apple vs. * debates", and about 100 people on HN would immediately start actively shutting down pointless Apple debates.
But he doesn't want to do that. I'm sure there's a reason for it. Part of it is probably that no matter what the ratio of light to heat, YC benefits from having HN active and perceived as open and unmoderated.
† Not interested in debating this; take it to 'pg