it's right to let the bank account get lower even when u leave the server with debts...i used to leave too, when i tried to win millions gambling and failed reaching the -1 mil debts, now is more realistic
but the lowest bank limit, must be set to 0 like someone else already said, this will let people try to earn cash again starting from 0, which isn't anyway a good prospective xD
but at least they won't leave the server, since they couldn't come back with a positive bank account, or create another account (even easier) to avoid the debts and losing their stats