Sure, and Harvard is supported by ads, you just don't realize it.
(sell an education->create wealthy people->ask them to contribute->get endowment whose returns account for the largest source of its operating revenue[1])
but I find your semantics frankly ridiculous. yes hacker news belongs to ycombinator. but you can't just use the word ad however you want. No, not everything's an ad, and in particular you can't 'buy' a job ad on HN. It's not a good description of the situation.
https://news.ycombinator.com/jobs