The problem with blacklists is that it's trivial to make endless domains to spam. The fediverse avoided this by being too small to matter , but as the reddit exodus begins this is about to change
yes, constantly adding new domains and spamming with them is a probably vector, but I'm not quite sure if that works due to how federation works. I am not quite that familiar with the implementations.
It's based on dynamic count. For now it's a very simple how many users per post there are and each instance can set their own threshold for it.
It's not about few users, it's about a tons of users and no activity. If you have 5000 users and 3 posts, it's likely those are all spam accounts. This is what we're checking for right now.
This is not a manual process currently, but I'm planning to add the possibility to whitelist and blacklist instances manually in the future.
It just means most of the people with principles have already moved here, or that reddit is engaging in disgusting levels of astroturfing. The latest Announcement is even worse. Regardless, it's just ruined.