Let's say I'm from instance A and use a community from instance B. Let's say another user of instance C, that's not federated with A but is with B, post in B. Can I see that post?
Let's say I'm from instance A and use a community from instance B. Let's say another user of instance C, that's not federated with A but is with B, post in B. Can I see that post?
My understanding is that defederation only affects content that's native to the instance that was defederated. So in your example, users of instance A and instance C would be able to interact on instance C.