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:
Aren’t admins already able to defederate, which is essentially, a fediblock?