With usenet you did give permission, the inherent nature of usenet required messages be copied across large numbers of independent servers with different access policies (free, charging, etc) and mechanisms (nntp, email, web). Hence by posting to usenet you implicitly granted permission for your message to be copied (this was actually tested in court a few times in the 90s).
> this was actually tested in court a few times in the 90s
Sure, I imagine the legal departments at places like Deja News were kept busy for a while as the practical nature of Usenet was debated.
However, I'm not aware of any case that was sufficiently broad as to support everything that goes on. For example, has any site that takes Usenet archives and slaps in-line ad links all over the posts, thus actually changing the content, ever successfully defended an action? Or any site that takes posts from Usenet, but keeps replies posted from its own systems on those systems only?
Inline content modification is one where I suspect the legal territory might be murky, however not propagating replies is almost certainly legal.
While posting on usenet gives an implicit licence to allow servers to to copy the message, there's no explicit or implicit legal requirement for an individual Usenet server to propagate replies. Indeed even historically there have been many usenet servers that were one way only due to the nature of peering arrangements.
> however not propagating replies is almost certainly legal.
On Usenet, possibly, but it is probably reasonable to assume that someone posting to Usenet knows that it is a distributed system and not all servers copy all messages, and therefore that by posting anyway any implicit permission to copy their material takes this into account.
On HN, however, a post is always accompanied by its replies. If someone posts something, and then posts a follow-up, they expect that anyone reading one comment can also see the other. Given that the entire legal basis for reproducing any comment from HN is built on implied consent, taking a snapshot that breaks that connection seems like fairly dangerous ground to walk on.
