CCP Video: Students critiquing essays

In this video, students have just finished critiquing a set of essays in small groups. One anointed member from each group was then brought to the center of the fishbowl to critique the essays in a student-led discussion.

What do you notice about the discussion?  What scaffolding and instruction (both on content and process) would be necessary to prepare the students for this level of student-led discussion on critiquing essays?