This is a good example of how copyright’s continuing obsession with ownership and control of digital material is warping the entire legal system in the EU. What was supposed to be simply a fair way of rewarding creators has resulted in a monstrous system of routine government surveillance carried out on hundreds of millions of innocent people just in case they copy a digital file.
This is actually a great question, in the context of the Fediverse.
Usually, every social network or forum has in their ELUA that anything you post is theirs, and you can’t do anything about i.e Reddit using your data to train AIs.
Hlwever, here, we’re on private instances of regular people. We can make our own rules, can’t we? If an instance would say that anything you post is copyrighted by the author, i.e by CC, would it be enforcable if someone would decide to scrape (or repost) the content for profit?
Both cases the author retains copyright.
So the question isn’t if ordinary people can exert copyright over their content, they absolutely can.
The reason people seem unaware of this is because the crux is that other then a rare exception no ordinary person can sue a megaorg like google or meta and win. For mostly trying to find a literal army of lawyers and corrupt bureaucrats would be mental health suicide.
That’s exactly how capitalism likes it and thats how they stay on top in a position to lobby lawmakers, which is yet another thing you are definitely legally allowed to do as an individual.
It’s not theirs. What you grant them is a non-revocable permanent worldwide license to use the content.
This is mostly necessary for the service to function, which is why it never really got pushback in the “early days” when communities were more tech literate. You need to be able to serve the content to users, and to a lesser extent being able to share popular active discussion topics is a big part of enabling the service to form communities.
What clearly isn’t necessary is the “non-revocable” part. People should be able to delete their posts, and excluding for the purpose of moderation, have them removed. What also would be part of an “ethical” platform (to me), is a clear restriction in purpose to that license. I would limit my rights to the ability to use the content for the purpose of providing the “forum”(/whatever), moderation, and sharing public posts/comments to attract people to the community. But that’s something that isn’t trivial to write a contract for, and it is worth noting that unless they gave away DMs (which is extra awful), all of this content was deliberately public.
You could, as a host of an instance, have mostly whatever terms you want. The code is open source and it’s not typical for open source licenses (including the GPL) to restrict things like that (you could probably structure a license that qualified as open source to prevent you from doing abusive things to end users of a service, but restricting how you serve it at all is unusual).