while I'm new on mastadon this is not my first rodeo with federated internet comm. there's a path this goes down, I expect mast is about halfway down it so far? you tell me

0) you have a network of federated instances, call them "foo", "bar", "baz", "qux"
1) admins at "foo" keep having to block users from "qux", cannot come to an agreement with the administrators, end federation with them.

2) "foo" also demands that the others block "qux" as well, or they will split with anyone who doesn't! "bar" follows suit, but "baz" doesn't, they too are blocked
3) this continues, yea, even unto the seventh generation. everyone who does not block all of the instances on the Bad List goes on the list. you end up with two (or more) fully disconnected graphs
4) default position towards new instances becomes hostile, they are assumed untrustworthy and have difficultly entering (email is here now)

5) eventually a new instance that has some unique selling point doesn't even attempt to federate, which also makes technical cost of improving network features way easier (this happened with xmpp, and sort of happened with irc)
6) legacy instances decline
7) eventually the whole thing starts again from scratch because we are in Samsara With Computers