There seems to be signs everywhere telling you this is not allow or that is strictly prohibited. At my subway stations one sign reads, “any behavior that might inconvenience another person is not allowed.” Might inconvenience someone? That kind of covers a lot.
About a year ago the subway authority began a new campaign: the Manner Poster, kicking off with the one below. New posters followed every month or so highlighting bad behaviors to avoid such as don’t put make up on while on the subway.
At the bottom, for the benefit of English speakers, is written: “Good manners are not rules. They are born from consideration and respect for the people around us.”