Febiblock is a useful thing that happens on other Fediverse social in which instance admins share their worries about users or instances. After a discussion where everyone shares their knowledge about the problem, admins decide if that instace/user must be blocked or not.
It could be very useful for the recent bot spamming. Since maybe the spam could be repeated on multiple instances, by sharing the emails/usernames those bots were registering with, admins could block them more easily.
More info:
I know Matrix instances use common ban lists as well. So if the matrix.org instance bans someone, it usually also means being automatically banned on a lot of other instances who follow matrix.org’s ban lists. A system like this might be useful alongside a wiki documenting bans.