Ah, this one is for historical reasons. IIRC Lemmy did not always have the option to block instances so blocking instances are purely local.

That being said, blocking instances in Summit should work. It just won't sync to web or other apps.

There is actually some benefits to doing it this way as it's compatible across different backends as well (eg. Lemmy vs Piefed).

Maybe a more proper solution here to do check if the backend supports it. If it does, use the server side block otherwise use the client side one. I'll add it to the roadmap.