It's a good question... We are actually in the process of shifting our current moderator model. We have an "expert solver" that sponsors the challenge and gives blanket advise to all solvers throughout the design process. So in the research phase, they might give students advice about what sort of information they should look for or in the "Connect" (Empathy) phase, they might give students advice about asking good questions... We scaffold the process so students submit work after each phase or task and teachers/moderators give feedback and award points based off of a rubric after each submission. That is the qualitative feedback students get throughout the process.
Love it Benjamin Plummer and totally agree. Have you checked out pblworks.org? We just wrapped up a pilot program with business students from Thomas University and our local tech school who solved challenges from the business community on our platform at tisktask.org. For some teachers it is a big shift, but they loved the reward of student and community satisfaction at the end!