I'm not sure from a mod or admin point of view (while I am a mod in one community as a backup, I've not done any moderating myself), but I know that if you block a person on your own account, the only indication they'd have is that you don't reply.

From what I understand it's actually quite a difficult issue to address on the fediverse, since content is mirrored on so many instances, deleting or blocking it on one would have very little to no impact on other instances, and obviously ban evasion is much harder to spot, since anyone can open as many accounts on as many instances as they like. I would imagine it makes it really hard to stay on top of shit that comes in, especially the worst things like abusive content containing children.