but anyway, I just rewatched that scene and Zhu Jiu goes back to the pillar with his face wound streaming blood to swear loyalty to Ye Zun

Oh, good point. I have no answers, then. (... Unless the Envoy was marking him as a criminal along the lines of the Five Punishments, but that's just random context-free speculation, and a cheek scar seems a bit non-specific for that, to my unknowledgeable mind.)

I wonder if this came before or after Shen Wei rescued Chu Shuzhi from the Regent's torturey prison sentence... like, maybe Shen Wei wanted to punish him for the murder without delivering him into Dixing's official criminal justice system.