[gioo]

I apologize, I tried to answer a broader question and somehow kinda missed the main point.

If you host your own Mastadon server, you can federate with everyone. Other servers will only block you if you interact with the nazis, child porn, et cetera. If you keep the problematic content read-only then it's gonna be fine. You can hide the list of federated/blocked servers, so no one will know (unless of course, again, you re-tweet, like, or comment something from a specific server).

There is no weird thing allowing transitive blocks, but mind that there are block lists so if your server is inserted in one you will be blocked by a lot of servers at once.