> Hacker News has plenty of its own echo chamber, no different to any other social environment.

Sure, but fwiw the HN echo chamber is organic. People choose to interact with people who have similar opinions, as they have since forever.

In contrast, the echo chamber on HN, Tiktok, FB, etc is architected specifically to drive engagement. You are shown more of the content that you react to, so that you won't leave.