Admins should be able to prevent federation on the public & network timelines from a blocked list of specific servers.
and from specific "bad actors".
I don't see why individual users shouldn't be allowed to interact with anyone of their choosing but certain things just don't belong on the public timelines.
I just realized this may be covered by the current blocked list.
We already support blocking bad actors: https://notabug.org/diogo/gnu-social/src/nightly/DOCUMENTATION/SYSTEM_ADMINISTRATORS/CONFIGURE.md#public
I think we don't have blocking for whole instances but it's trivial to add...