I understand that cross posting is not always desirable, but it has it’s benefits also. You can find new communities, you can easily post a post which someone else posted into a more appropriate community where more people will be able to read it. For that it would be nice to consolidate cross posted posts in the view so they don’t show up over and over again but also have a way to cross post in a simpler way.
Taking a look at those two paradigms, I think I prefer the collapsed comment sections. Different communities/instances can have very different moderation policies or standards of discourse, so allowing users to segregate the comment sections like that would be helpful. Having all the comments from the different crossposts is definitely nice, and a step up from the way lemmy handles crossposts.
A special case might be if there are crossposts within the same community. In one of the communities I mod, there are recurring posts where the same lead image is used, so they are automatically detected as crossposts in lemmy even though weeks have elapsed since the last time it was posted. Not sure if something like this should be handled differently or not.