There might be a need to handle the cross-community spammers on an instance or Fediverse wide level though, in particular the ones who post to any porn community with the same title and picture regardless of the picture/title being on topic for that community.

The downside of that is that a lot of OF content is posted to dozens of communities and this fact is the main spam problem with them, not necessarily the content in any particular community on its own.

You can easily look up the owner of the IP address space to get the provider.

Caching has other downsides though, mostly for content that might not be legal in an instance’s jurisdiction.

Actually that is not really how Lemmy works. As long as at least one user from here subscribes to a community from there the community is right back in All here. And if no user is allowed to subscribe to something there you don’t really gain anything from federation.

Actually it would still show up in All as long as at least one user on this instance is subscribed to a community on the other one. Just not in Local.

The problem is that some of the categories of images that people might not want to pop up in their feed are very vanilla, e.g. dick pics are not kinky or extreme, just not something a lot of straight guys and lesbian women want in their feed. So should they also not be posted? What about feet? Some might not want giant pictures of feet on their screen. Or maybe rough sex? Some people also really don’t like cuckolding, so no pictures with captions or post titles for that? Where does it end?

It is not as if an instance is a legally distinct entity.