HN's core audience migrated from reddit after it became victim to the eternal September effect after it went mainstream. Reddit's core culture is the same as HN's - which is to say liberal, atheist, materialist and STEM-fetishising, and drawn to geek culture/media. Demographics-wise, white males from the US, predominantly urban/city-oriented. The main difference is that HN is more technical, and probably older because of said migration.

My experience with people being toxic or negative or whatever has been mainly people being passive-aggressive or hostile, regardless of politics. Most reactionary content here just gets flagged into oblivion regardless of how it's presented, of course. So the unpleasantness that actually sticks around tends to be either apolitical or liberal/progressive (I find neoliberals are too busy trying to make money to engage in petty arguments!).