Nothing magical or superpower about it. Maybe Eliezer isn't so good that he can get himself out with just one line; certainly, one would think that forewarned is forearmed and that a simple resolve to type the necessary line is enough to win every single time and that it'd take several lines to sink a hook into someone so they'll continue the conversation.
On the other hand, people writing about psychopaths have, for at least as far back as Cleckley in the early 1900s, marveled at how psychopaths can manipulate trained experienced doctors and nurses who know in advance that the psychopath is a diagnosed psychopath and will try to manipulate them. So clearly there are hard limits to how much good forewarned does you, and those limit are distressingly low...
Nothing magical or superpower about it.
It certainly fuels a sense of awe and reverence for his alleged genius. All for an achievement that can't been verified.
And then he boasts about being able to perform an even much hard feat, only if the stakes where "sufficiently huge", but when shminux suggested seeking actual people who could provide these high stakes, he quickly backpedaled handwaving that those people had some problematic features. So if you combine the two comments, he said that he would play that game only with the very people h...
Update 2013-09-05.
I have since played two more AI box experiments after this one, winning both.
Update 2013-12-30:
I have lost two more AI box experiments, and won two more. Current Record is 3 Wins, 3 Losses.