I'm not directly involved in either project beyond reporting bugs and suggesting features yet, but I follow both projects closely. My sense is that the Mbin community is prioritizing collaboration around UX improvements while Kbin is focusing on scaling/performance issues... which makes sense as kbin.social is more than 10x the size of fedia.io (https://fedidb.org/network/instance/kbin.social vs https://fedidb.org/network). I opened a bug about the UI for altering link images at https://codeberg.org/Kbin/kbin-core/issues/1365. When I tested the same steps in Mbin, the issue i was seeing in Kbin had already been solved in Mbin.

Kbin is a great PHP implementation of ActivityPub for reddit-like communities, but requiring all major changes to be made/reviewed by a single person is a real bottle neck.

It would be great if Kbin could figure out some form of goverance/delegation that would allow more contributors, but there doesn't seem to be much interest in that type of change so for now we have 2 project with different priorities and governance models... and that isn't necessarily a bad thing.

Interstellar app will not work on kbin.social, because this server has not opened its API yet. For the app you have to use either a Mbin instance or (for vanilla /kbin experience) kbin.earth

Unless fedia.io has blocked or defederated with kbin.social, you should be able to fully participate in those kbin.social communities from fedia.io

I’m on a lemmy server lemm.ee and am able to see and comment on this post in kbin.social. That’s the beauty of the fediverse.

I think the newest features available in Kbin are not available on Mbin.