well im sure there is a rule about account sharing. maybe its not enforced here for forum accounts.
but tis a standard anywhere on the internet.
and even if he didnt intend on breaking a rule, its his responsibility to secure his own account, not badspot's to clean up the mess.
He certainly should have secured his account, but as I said, I don't see how accidentally letting your "friend" into it one time is worthy of a
permaban (though if he had actually been sharing his account it would be suitable IMO). A warning or temp ban of some sort as a way of saying "hey, be more careful", yes, I could see that as a reasonable reaction - but just banning him forever right off the bat? Seems ridiculously harsh.