I think one of the biggest changes has been the visual deemphasis on individual identity in modern social media over forums, even on HN. Forums that allowed user large user avatars, flair, and the rest made it possible to easily visually identify back-and-forth between people, as opposed to reddit which deemphasizes usernames. This basically means that it’s harder to identify users across threads, and harder to “get to know people”. You may or may not have read my comments before, but you don’t instinctively make the connection between my past behavior and my present behavior unless you go look at my comment history or unless I’m one of the HN super-posters who gets mentioned by name.