Don't know if it was a tactic of Dukes, but a couple of times he made this move which cost me a fair amount of chips. No idea if it was that he had hit or just gambling.
I am first to act, lets say i have a reasonable preflop hand like Queen - Ace and I make a raise 3 or 4 x big blind. Duke calls. Flop comes and I don't hit anything.
Lets say it is

Duke is first to act and goes all in. I can't call in this situation and fold. Even if he has only hit bottom pair I am only 25% to win.
Might try this tactic and see if it works.
Yeah its called a stop and go, and the Duke appears to be a master of it. May favourite part of the game was when I had you slightly out chipped and reshoved on you a couple of times, then EricStoner had slightly more than me and was reshoving and the Duke had slightly more than EricStoner and was reshoving on him. Its like a wheel of death.