I have just logged in on my own Lemmy instance, and I see a list of banned users in the administrative area, from other instances. I have not banned anyone myself.
How does it work? If you’re banned from an instance, you’re banned from the whole federation?
And that would mean I can set up my own instance, ban e.g. you, and you’d get banned on other instances as well. That doesn’t sound like a well thought out design choice.