Like a list which instances interacted with the current ones, or are blacklisted. If there is no way to find out, then there should be (imo)

I think it would be an important information, and using this a graph of instances connected could be created, which would be super useful.

I understand that instances decide that some others should be de-federated, but it feels wrong that the instance maintainers have the power to do this (without asking the users opinions). I have no better idea though