Can a marshal add double his Charisma modifier to his Diplomacy skill?

Question

Can a marshal add his Charisma modifier twice to Charisma-based skills like Diplomacy?

Answer 1

Yes

The marshal needs to select the Motivate Charisma minor aura:

A minor aura lets allies add the marshal's Charisma bonus (if any) to certain rolls.

Motivate Charisma: Bonus on Charisma checks and Charisma-based skill checks.

If the Charisma bonus that you normally add to skills did not stack with the Charisma bonus from the ability, there would be no need to say "and Charisma-based skill checks."