Suggestion: Thread Entanglement, or automatic merging of duplicate threads en (kbin.social)

See the quick inspect-element mockup I put together for an example. I'm bad at design, but I think it gets the point across. Current implementation on left, suggested on right. Also, I'm using Kbin Enhancement Suite for the modifications to instance names, but I think they are even more useful for this demonstration.

How it could work: If the same link is submitted across multiple communities in your current view (subscribed, favorites, all, etc) within a certain time period (probably 24 hours), then have them automatically group themselves into the same box, along with a brief list of the duplicate threads and instances. Use whichever of the threads has the highest score as the one to fill the title and thumbnail for the grouped thread.

I didn't make a mockup for this, but when clicking the thread, it could then import the comments from each of the grouped instances. Options on the sidebar could show you each of the instances whose comments are being shown on that page, along with an option to filter them out of your current feed, and options to add your votes to each instance's thread.