The polite traffic jack-ass

Cut someone off in traffic, poke your head out the window, smile and wave… what’s up with that?

One: the gentleman was a vistor from New York City, understood my eye contact as a stipulation to yield, interpreted car lengths like we humans interpret dog years, and was thanking me for my generous nature.
Two: the gentleman knew he had cut me off and was thanking me for not making his car more compact.
Three: the gentleman was no gentleman at all, knew he had cut me off, and was rubbing salt in the wound.

You must decide.
(Not really.)

Give the gift of words.