My hot take is that I don’t like cross posting or reposting. I subscribe to communities for the unique content and perspectives that each one provides and to see a user posting the same thing to five different communities for whatever reason (getting upvotes seems to be the only reason) seems silly to me. Let go of the ego a bit and this need for internet points.
Depends on how you're doing it. It's common to be subscribed to multiple versions of any particular community and those cross posts will show up alongside each other in the feed.
I think that this is only a UX issue. Some users don't want to see the same post posted more than once, certainly not few times in a row.
On the other hand, significant discussions could develop inside each of the posts.
Cross posting should have their own view. Maybe aggregate/group posts with the same content, and allow switching between comment threads(root comment as well) inside the view.
On the feed, all the subs where it was posted could be shown underneath the main content with the other meta data.
At any rate, I do strongly believe that cross posts should be handled differently than regular ones. The platform should be aware of duplicates.