Hacker News in absolutely no way shape or form has an algorithmic system on the same level Facebook has, it is manifestly a bad analogy
A possible question of interest, were this lawsuit to find Facebook guilty, is "If someone somehow gamed HN's algorithm (which is relatively simple, so would in practice be pretty easy to game) to encourage a genocide, should HN be liable?" How complicated the algorithm is likely does not enter into the reasoning for culpability.
If your targeted algorithm makes the company money off planning a genocide, and if you're aware of it and do nothing about it (because lawyers say blah blah section 230 blah blah), that's a real problem. If you're making money from people whining about a bad call in a football game, so what? But if your company actively promotes criminal content and profits from it, then section 230 probably isn't going to save you. Either it will change, or the courts will force you to.