Objectively speaking, Duncan was truly sincere at the time—he greatly admired the tenacious and straightforward Judge, appreciated her performance in that disaster, and even beyond this admiration, he valued Vana as a special "node" very much.
If it were not for sufficient coincidences, it would not be easy to place such a "node" among the top echelons of the church, and it was even harder to establish the most basic "friendship" with it.
Vana was very straightforward, which determined that she would not deny Duncan's merits in the protection of Plunder, decided that even if she were personally awkward, she would be fair about this "great favor."
It's just that Duncan's sincerity, to others, might seem somewhat frightening.
