Aziraphale himself has been vaguely aware of more powerful - or, at least, with some form of power - creatures in the train ever since the last stop, a couple of which he'd actually met in person. So far, only one of them had given him alarm (though not by any fault of their own), and the signals do eventually blend into the background when the angel isn't really paying attention to them.

He'd take note of it now, probably, if he didn't feel terribly embarrassed by what's happening.

"Oh, thank-- thank you." A compliment is a compliment, after all. "Don't mind him."