@maloki @HerraBRE spammers are clever. It's easy to create an account on any server, and before a moderator have the time to react, the spammer have sent messages to most of the fediverse. What can the moderator do? Block the account of course, but by then it'll be too late.
They could block the instance as well, but such heavy handed measures will impact all other users of the instance.
I can think of solutions but they would require protocol changes.