Granted, but then, perhaps, teachers could incorporate a 'non-judgmental' form of peer review, as a way of teaching students how to give constructive criticism and positive feedback.

In which case it wouldn't serve the same purpose I'd originally suggested, but it would still use this opportunity to teach something useful. I'd go with: students conduct peer review by writing comments or suggestions for their group members. The teacher then grades each student (probably in a 'check-minus, check, or check-plus' simple scheme for whether or not they did it at all) based on the comments they GAVE, not on the comments they received, and gives the students feedback about the feedback they left...if you get my drift :-)