I was there for his pycon talk, and it seemed to me (they stood out for me as well) that he was using disfluencies to express disbelief or punctuate something extraordinary or unexpected with humor. I do this too? But instead of uhm, I'll end a statement on a rising tone as in an interrogative?
You’re in good company. The rising tone at the end of a sentence used in a non-interrogative context is called uptalk or a high rising terminal [1]. Its increased use has been a far-reaching dialect shift that has been ongoing for a couple of decades now. The New York Times published an article on it in 1993 [2] and just recently another [3] with a good overview of how its use has mostly spread into every corner of the American populace. Perhaps my favorite discussion of uptalk is an analysis of some of George W. Bush’s speeches in which he extensively employs it [4].
