Global Blacklist
The Global Blacklist is an opt-out feature which prevents flagged users from joining your server. This is reserved for users who are significantly violating Revolt's ToS and are pending termination. In reality, it's unlikely that you will ever encounter this.
AutoMod will show a warning on a flagged user's infraction list:
Unless you're opted out, the user will get banned immediately upon joining:
If you wish to disable this feature for your server, run the following command: /botctl ignore_blacklist yes.
Since I'm essentially elevating myself to platform moderation with this, I want to be as transparent as possible about it. This will only ever be used if someone is posing a serious threat and if I'm not able to immediately contact a platform moderator.
You can always retrieve the complete list of flagged users via the API at https://api.automod.me/stats/global_blacklist, and read the relevant source code (botadm.ts, event_handler.ts).