If they started banning people due to multiple accounts then 90% of the Regnum community would have to be banned. Including those sharing accounts. That means... Every clan that has banks, every person who's ever accessed those banks, anyone that has bank characters of their own and anyone who made an account before the additional slots were purchasable to have the other classes. So yes go ahead and start banning people. Please.
You'll lose 50% or more of your entire game community.