I agree that the original article type and article author should be copied, when “Split” is used.
But as this would create an incoming e-mail-ticket in your case, it would also re-trigger the “auto reply (on new tickets)”. Which might be intentional, or not. So with your suggested change, we also would need a condition in triggers to detect if a ticket is “created” or “created by splitting”. In which case, you can actually automatically inform the customer, that a new ticket was created because of the splitting, to make sure he answers to the correct ticket number if he wants to add some information.