@evan That seems like a leading question, please let me know if I am misreading you.
I can outline many ways in which Fediverse posts are not collected the way items would be in a library and how we determine ownership or lines of stewardship differently from how a library would.
As others have said, if posts are collected even if a user has them set to auto-delete after a certain amount of time (a mechanism baked into the Mastodon platform for example), that seems like overreach to me.