What is the most absurdly specific etiquette rule in your world?

Okay, I’ll start! In my world, there's this rule called the Gloved Knuckle Clause. Basically, any noble has to tap the third knuckle of their left hand three times on the table with a gloved finger before talking to someone they see as an equal or superior. It's a way to signal "readiness for discourse” without coming off too eager.