For example, say an instance C is not defederated with B nor A. Can a user on A see users from B if they visit a community on C? If so, to what extent can the users from A and B interact with each other on C?
My understanding is that the “host” instance of the community is responsible in sending things out to the subscribers. As such, when users from B post on a community on C, C will broadcast the activity of user from B to instance A’s federated copy of community on C, and users on A will see the post from the user from B. They should also be able reply to each other’s comments on the community on C.
except instance A will actively reject such content from B users when it hears about it from C.
generally it should be expected not to see any new content from B, but historic content will still exist and basically be in a frozen state.
From practical example:
I defederated one instance. Before, I saw content of them, now I dont. I dont know if they can see my content but I dont think they do.
Obviously a sample size of one is not evidence but more of a hint at what might happen.
You can always ask the folks on .ml for they make the software.
