This is an interesting analysis! I would be interested in your post. :)

My theory is that he was probably leaning on Professor Shen to be able to bear this particular humiliation upon himself. Even though Hei Pao Shi is a persona it is still tied in part to who he is, so even though such a demand to kneel would be humiliating for anyone, it is even more so for him.
True. Professor Shen is capable of bowing to Professor Ouyang and doing the necessary social things. The Envoy bows to no-one.