[conjectures]

You can't really have a discussion by everyone posting on a separate site.

So I guess it boils down to whether things you type on HN are discussion or 'content'.

[laumars]

There are federated platforms that let you do this - or at least a lot closer to that kind of reality than a forum / HN style site does.

You do make an interesting distinction though. My counterargument would be "Ask HN" style topics where the entire content is hosted on HN - however I don't disagree with the point you're making either.

[em-bee]

can you point to some good examples of how that looks like?