Is two-way authentication possible between a wireless power transmitter and receiver without compromising WPC communication?

Two-way authentication requires communication between Rx and Tx, while WPC only supports Rx- to-Tx communication.  So by definition, two-way authentication is beyond the scope of WPC’s standard protocol, but including this “beyond-Qi” feature will not compromise the normal Rx-to-Tx communication required by WPC to module power delivery.