I have not been following the exchange very carefully but have read the authors' replies to Dick Posner and to me. I want to amplify my earlier point, that studies of law student responses to abstract problems about ambiguity have limited (perhaps no) value in understanding how judges, administrators, or even practicing lawyers process issues of plain meaning, ambiguity, and statutory interpretation.
Limitation #1. As Aristotle said (paraphrased for the current debate), statutory meaning is driven by context--including the facts of the case, the policy and legislative background, the surrounding text and the whole act, precedent and other prior interpretations, the constitutional terrain, etc. Simple hypotheticals have limited utility in telling us much about how judges et al. evaluate statutory texts--but perhaps the more telling point is that judges et al. have a lot more experience with legal materials than first-year law students do.
Limitation #2. Judges, administrators, and (usually) lawyers are publicly accountable for their interpretations of statutory text. That the law students answered the questions anonymously (I assume that was the case) or surely with no public accountability makes their task much different from that of the judge who realizes that her interpretation can be criticized by the losing party, lampooned by commentators, or reversed on appeal. Do these features of professional practice suggest that judges will be more disciplined than law students? I'd assume so. (This calls forth my biggest surprise about the study we are discussing: without accountability, I am surprised, and impressed, that the law students were not more influenced by their views of the merits. Good for them.)
Limitation #3. Judges, administrators, and attorneys also usually provide reasons for their decisions. I wonder whether the requirement of reasons might exercise some discipline on respondents, independent of the accountability point.