If you were eating a basic (nothing exotic) rice ball (onigiri), they would not look twice. Can you guess why? Smell. (You also did not mention if fries were included.) My advice: Eat the hamburger on the platform and take the next train. Or, try something with almost no smell.

It's common to see parents feeding onigiri to their kids on the train, even if it is "technically" (the best kind!) against the rules.

And if they were eating durian, everyone else would gang up on them and throw them off the train.

Even a durian crazy country like Singapore explicitly bans them on public transport, definitely won't blame the Japanese :)

I never thought of it before, but I don't think there is any food you can buy at Japanese station-platform kiosks that really smells. Very different case in Korea. On long-distance trains, there is always that guy with a bag of dried octopus...

Sometimes I’d shop around for a car or two for a perfect, heaven mandated seat for me, when the train isn’t leaving soon anyway.

It should be no big deal, unless people are really keeping distance from you and standing in the next blocks of seats. That happens, like, a man with garbage bags is grumbling nonsense. Bags of fries and 551 takeouts at 5PM usually won’t trigger that… just appetites :p