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.
"It wouldn't make a difference" - To whom? And how do you know? Even if a bot passes the Turing test, a community where there isn't any creativity or new information will die out. LLM is not the be all and end all of the human experience.
To take it further. even if we were all in the matrix, the statement "it wouldn't make a difference" is not true - philosophically speaking.
Also, humans have a circular reference with society at-large. Humans shape society, and society shapes humans. So something completely different might shape future societies, but I'd rather discuss the situation as it exists today, rather than an imagined future.
I'm not sure the same is true in 'real' communities.