Of course, if they were going to disallow lighters and matches on board, thanks to the shoe bomber, why and how would they allow smoking anyway?
But seems to me it’s been generally disallowed anywhere. China has some very nice, very big airport terminals nowadays and I don’t recall anyone being allowed to smoke in the general public areas in any of those either.
Are you talking from your own experience??? IME e-cigs vapour smell ranges from non-existent to sligthly reminiscent of whatever the e-cig is flavoured at (coffee, fruit, etc…) and even in the latter case doesn’t linger on. Vastly less noticeable than, for instance, people’s anti-perspirant or perfume.
I strongly doubt that you could smell it on your clothes, especially two weeks later.