Memes

I think each title/post of the same content should be treated as its own top-level object in the comments section, so collapsing everything at the top level would show you all the posts and reposts from various communities.

On client side, you should be able to merge all the posts, to sort all top level comments together. But if you go to make a top level comment, you'll need to be replying to a specific post from a specific community (selectable, but defaults to the title you were shown from outside the post).

From outside the post, I think it would be cool to be able to browse the various posts of the same content from different communities, seeing their titles, the name of the community/instance, the number of comments.

Just my initial thoughts. Mainly, I just think it's cool that we're talking about this issue at all because once we solve this kind of problem in all its forms and iterations, we could see some really cool decentralized communities start to coalesce. IMO, the next big step after this would be building systems a user could use to find instances and communities they're not yet aware of.