>They don't make a dime off of this, as far as I can see.
Maybe not directly, but every YC company advertises themselves and their projects here, and HN is known as the hub for the SV tech and startup scene, which gives YC an automatic amount of "street cred" and visibility in all of the discussions had here. I'm sure Hacker News has made YCombinator more than a few dimes indirectly from all of that.
In general internet communities face a trade off between monetization and quality. The more you monetize a community the crappier it becomes. In the long term, the key to running a healthy online community is to find a good balance, which essentially means figuring out how to not make too much money.
Maybe not directly, but every YC company advertises themselves and their projects here, and HN is known as the hub for the SV tech and startup scene, which gives YC an automatic amount of "street cred" and visibility in all of the discussions had here. I'm sure Hacker News has made YCombinator more than a few dimes indirectly from all of that.