Security needs to be tightened

It should be impossible to create multiple account in a short time from the same IP.
It should be impossible to use the same username or visually similar username as existing users.
It should be impossible to claim a bounty less than 48h from the account creation.

A bounty of us is getting hammered by morons, creating claims with fake accounts impersonating other users: this should not even be possible by bounty source.

Please do the needful to prevent these behaviours.