Rather than try to act like a link aggregator where people submit links to articles and images and that submission comes with a comment thread specific to the fediverse instance in which it was submitted, what if each news site, image host, blog, whatever was itself the instance and the reddit-style instances federate with those. Someone submits an article to /m/news and the comments link goes to the instance associated with that article. Submission is the act of 'bridging' the article's instance to yours. Everyone sees the same comment thread and it's tied to the article itself. Comment on the article via kbin and everyone sees your comment. Perhaps the user can also see what other communities/instances where the article has been posted, and perhaps comments could be filtered by user instance.

Could also have instances have separate comment sections that don't go the main one for communities that prefer to have insulated discussion (the discord effect, where you can share a link with friends and be assured that everyone can chat about it in an isolated environment), like "forking" the article.

I can see several benefits (and a few potential issues) with this, but it seemed like an interesting idea at least.

Obviously the biggest issue with this is getting the content sources on-board with acting like a federated server. But then again, tons of major sites use various third-party tech for comments on articles...