Everyone deserves to reward themselves with a great meal. That's true even on the subway. Who knows how long your commute might be. Sometimes the only way to unwind after a long day of work is to eat a leisurely meal. Who cares that your leisurely meal takes place on a moving train? You have to make life work for you. This guy is making life work for him so well that I'm actually kind of jealous of him. Fiji water? That's like the best water. Chopsticks? The best food are eaten with chopsticks. This guy is killing it.
I wouldn't put it past someone to sit on his tray thinking it was a seat. Then what are you going to do? I think crying sounds like a valid option. Sometimes your only options are to cry or to punch someone.