That may be technically true, but is really just an implementation detail. If HN quietly replaced all the accounts with suitably capable LLM bots, it wouldn't make any difference. What this type of service really has on offer is solitary activity: Writing for one's own enjoyment, differing from a private journal only in that the software here provides some colour back to spark additional thoughts in order avoid writer's block.

I'm not sure the same is true in 'real' communities.