I'm wondering what the whole story is. I can't imagine someone just deciding to demand a D1 seat, especially when the D1 cabin is full. Was the guy downgraded at the gate? Did he have a GUC fail to clear and then saw a nonrev get a D1 seat? Or did he see the relief pilot resting in a D1 seat and misunderstand the situation? Did DL kick him out of a confirmed D1 seat to create space for a must fly mechanic? [A different TPAC flight had mechanical problems on July 3rd, so it's possible that a mechanic was needed in Tokyo. I also know that westbound TPAC flights on July 4th were surprisingly full in D1.] Or did he ask the purser why he wasn't upgraded and the purser decided to go on a power trip?