HN is a bubble where people listen to what you say even if you argue against them, I haven't found any such place anywhere else before. I've found some people who listen even to people they disagree with on some niche forums, but never a community as big as this with density this high.

Other than listening and arguing in relatively good faith I don't think HN is a bubble, although such people probably have pretty different opinions than the typical person simply because they listen and change themselves more so it gets more refined.

But isn't that the definition of a bubble - a group that doesn't behave the same as gen pop?

I would say this is the definition of a sub culture.

A bubble in this context has the connotation of ignorance of what is outside the bubble.