To add on to this: Instance admins have no control over moderating content from other instances that they’re federated with. An acceptable post on one instance could be rule breaking to another. The only option that other instance has is to defederate. Admins have acknowledged defederation is an extreme measure for what is often just a few problem communities or users, but they have no other option.
They can certainly remove and ban specific users, so it’s not like they have no moderation tools. Defederating is usually the nuclear option when you have instances with things like bigoted content or that doesn’t properly vet its applications
To add on to this: Instance admins have no control over moderating content from other instances that they’re federated with. An acceptable post on one instance could be rule breaking to another. The only option that other instance has is to defederate. Admins have acknowledged defederation is an extreme measure for what is often just a few problem communities or users, but they have no other option.
Is there not an option for blocking just that problem community or user?
They can certainly remove and ban specific users, so it’s not like they have no moderation tools. Defederating is usually the nuclear option when you have instances with things like bigoted content or that doesn’t properly vet its applications