Content shouldn’t be crossposted between communities
At least not systematically, and not within a day of the original posting (so if something becomes topical)
First community to post a content have “authorship” of that content
It's not a dibs system, so organic collisions where two people really want to talk about something is fine. just systematic reposting of EVERYTHING from people without their consent isn't good for lemmy.
Communities that repost content from other communities should be closed. Admins should close communities that do so.
Not closed, the reposters should be be given opportunities to transition to their own content.
People will have to subscribe to all the similar communities on one topic to follow all posts related to that topic
That is a direct aspect of the lemmy model, until such a time as themed communities becomes protocol level. The only way to not have to do this is kill any similar community before it grows.