I don't stealth vape, but I am discreet about it in airports. No one has ever approached me, but on one long layover I did hear an overhead announcement "Reminding all travelers that the use of cigarettes was forbidden in the terminal". Dunno if it ran at intervals or if someone reported me...
It depends on the airport. If I'm in Charlotte, where the terminals are cramped, I tend to not do it. If I'm in a nice airport with lots of room, I just tend to find a quiet area.
I'm very much of the opinion that if it isn't bothering anyone, it shouldn't be a problem. That's mostly what I've found...
And on airplanes, I've been known to go to the lavatory on long flights. It's certainly a better cloud to leave in there than what most people leave....