When a Bdc representative turns over a lead to a salesperson, the messages should always go to the salesperson. When a BDC rep. responds to a message from the customer, the customers responding back will send the notification to the (Bell) notification tab instead of the message tab on the salespersons end. Once the salesperson re engages to the customer he or she will start receiving messages back to the appropriate tab.

(In my opinion) once a salesperson is added to the deal, the messages should always go to them in the message tab no matter who is responding. It should never go to the notification tab, unless it's an opened email.