@stux One poorly understood feature of federation is that blocks aren’t transitive. If I’m on instance A and my instance blocks harmful instance C, but your instance B does not, then my posts can still reach instance C if you boost a post of mine and someone from C follows you. If my safety depends on my posts not reaching C, then your instance’s choice to not block can be a threat to my safety. A lot of my attitude to instances that don’t participate in blocking the worst actors stems from this scenario.

Not saying that this is what happened in the case you’re thinking of, but few admins think of this angle and are surprised when I point it out to them.