Bosala's reaction to the Duchess marriage?

When the Duchess admits that she is married to Antonio, Bosola pretends to be filled with joy and admiration that the Duchess would look past rank and wealth to give a man his true due for his character alone. The audience knows not to trust his effusive praise, of course, but it is worth noting that the final tragedy for the Duchess and her family comes out of this very moment, when Bosola uses this praise of looking beyond rank to get her to admit who her husband is.