You ask good questions, but I'm afraid they're very hard to answer no matter what the admins themselves believe to be morally correct.
Most of what you refer to is essentially a copyright issue. Unless otherwise specified by the copyright holders/creators of a piece of work, you're not allowed to repost it. In most jurisdictions this is very straight forward. The problem is enforcement, obviously: how are you going to verify that every OP has the right to share the material they're sharing? Excluding OC, you'll find they probably don't. Really determining this is very time consuming at best and impossible at worst.
So I don't think it would make sense to have a strict "you can only post OC or content you have the rights to" because it's just not compatible with a platform like Lemmy (or Reddit, for that matter). And if enforcement is more or less of the table, you might as well not have such an explicit rule and only respond to complaints 🤷
This might just be me, but does anyone else have the issue that videos can't be opened within the lemmy interface anymore? When I click on a video hosted on files.catbox.moe, it just doesn't expand anymore. It did that yesterday...
Also, I think I saw on another instance that redgifs Videos could be expanded in the interface as well. Was that added in a newer version? If so, it would be really cool if this instance could update.
Hetzner (server provider/hoster, not ISP) has strict no-porn rules. So even if you run the most vanilla stuff you can get booted from their service.