there may not be an algorithm at work here as there is on Instagram or TikTok, but there's still a bubble - the name, design and discourse of HN itself works as a filter.

What you're describing is an echo chamber, when people willingly share only things that they know resonate with the group.

While still somewhat detrimental, it's at least a visible problem - everyone is aware of it because everyone sees the same thing.

With filter bubbles, you create personalized echo chambers, that nobody is aware of unless they're in there.