I think it would be very useful to be able to browse communities by instance. For example I’d like to be able to search an instance name and get a list of all the communities @ that instance. It would help to get a feel for the vibe of a particular instance without having to leave the app, and also be good for community discovery.

Another way to do this would be to be able to browse the Local feed of another instance than your own, but I can imagine that this would be more difficult to implement.