I think Lemmy should come up with a meta cross post type. Where the post only exists once, but it’s indexed in multiple communities, and moderators of those communities can remove the cross post. Without affecting the original post
Some discussion about how crossposts could work differently
If not that then give us the ability to have relative references to posts inside of Lemmy. Instead of referencing a URL to a specific instance, kind of like the ! Or @ for for community names and usernames.