> why don't we apply PageRank for every user based on the upvotes they receive for the comments they leave on any post<p>Absolutely not, think about the incentives this creates! Imagine yourself to be an adversary, how would you game this system? <i>Easy</i>: spam low-effort highly agreeable comments across the site. The more the better, they're basically guaranteed to get <i>some</i> upvotes and boost your karma. Now, with your newfound power, you can shape the HN front page to your will.<p>Instead of the front page being a signal of quality, it would be correlated to the posters' karma. And because the front page is a limited resource, you basically get a crappier version of Twitter where relatively low-karma accounts have practically no chance to get on the front page even with high-quality posts, and high-karma accounts will be able to roll their front-page posts into even more karma. This is pretty much one of the biggest flaws of major social media websites today: they concentrate power in a few users with massive influence.