And it's not just human moderation (which would be biased based on the moderator) but things like the flamewar detector which actively demotes content that is getting a lot of quick responses. This is precisely what Facebook would promote, and HN might also if they were dependent on ad revenue to fund the service.

Much of what's bad about Facebook and other social media pretty much boils down to their need to show as many ads to as many eyeballs as possible.