To mitigate spam, I wish servers that allow signups had a probationary period where people can only post to their own profile but it only sends out notifications to their followers in the beginning. If they mention someone, it doesn't send a notification (or perhaps puts it in a queue that will only be released after a moderator or admin approves their account). Because the current vector of attack seems to be mentioning popular accounts.
This allows people to sign up immediately and start using their account, but they can't spam others since only their followers will see their posts initially. It also gives admins and moderators the ability to look at real content to see if they need to be approved or banned.
Combine this with other methods, and we can reduce spam, even on servers that allow instant signups.
