The most effective Feedback requires both parties to be vulnerable with one another.
Real personal feedback is uncomfortable. You have to put yourself out there, both as the feedback giver and receiver, if you are to have effective feedback. The best feedback comes when both parties are sitting on “the same side of the table” (either literally or just metaphorically) with the problem in front of you both, but not between you both.
Grades are easy. Performance scores are easy. But those things don’t create the kind of feedback that leads to growth (for the students OR the teachers).