You wrote of U: "This one is a real beast, with code more that twice as long as that of its competitors. It actually models the opponent's behaviour as a random process specified by two parameters: probability of cooperation when the second strategy (which is the RackBlockShooter) also cooperates, and probability of cooperation when RBS defects. This was acausal: the parameters depend on RBS's behaviour in the same turn, not in the preceding one."

Isn't that just a simple bug in U? Probably Nic Smith meant it to model the opponent's responses to U's behavior on the previous turn, not the correlations between their actions on a given turn.