(a) HN is the front-end and back-end of a bunch of YC business processes.
(b) The voting ring and antispam features rely on obscurity; they are game-able.
The code for older versions of HN is available, but you'd be better off with the code for lobste.rs.
It's just that if you're in a YC batch or an alum you get posts, especially job posts, boosted.
I wouldn't pay much mind to this talk of mechanisms and gaming systems, sounds like post-hoc reasoning by outsiders.