One that happens in the story: When Shen Tai is in a heated discussion with one of the Beloved Consort's most trusted servants, and ends up using a gesture that carries a meaning of, roughly, "Be silent." Since as far as Tai knows, the only "rank" he has is as an officer of one of the army divisions (and it was essentially a political appointment, at that), he then spends a couple of moments expecting to be reprimanded for rudeness, at a minimum. Then he realizes— since his sister was declared a princess, to help justify her participation in an arranged marriage, her family can now be treated as royalty, and this includes him.
The servant could, arguably, get away with his actions only because he directly served the consort of the emperor. There is almost no higher authority.
At one point, Prince Shinzu politely asks Shen Tai to consider gifting his horses, where most of the officials Shen Tai had met demanded the horses. But, given how long Tai's trip had been to that point, the prince had possibly already received word that Shen Tai was thinking of gifting them to the Emperor- Shinzu's father. At worst, the Prince would just have to keep quiet, and he would get access to the horses anyway. He can afford to be polite.
Logic:
The gift of horses gets discussed, with Tai openly wondering if the princess had any idea of how receiving that many would upend his life. The consensus is that, since she's royalty, it may not have entered her mind.
Horror:
If Pei Qin hadn't heated the wine improperly, then he wouldn't have been in a position outside the First Minister's property to pass along messages. Tai was only able to tell Lin Chang (formerly "Spring Rain") to leave the capital because he was able to slip the ex-servant a message to pass on to her. If he wasn't there....
