There are many benefits to peer feedback, just like there are benefits to using multiple choice questions. However, like for MCQ, my motive for using this more in my classroom was Grade 6. Four sections of Grade 6. Ninety-nine students. Which is a lot of rough drafts. Which is a good reason to delegate some of the feedback burden.
But there are other bonuses to using peer feedback. The students can read the work of their peers, to give them ideas for their own writing. And, by leaving comments, they can reflect more on the characteristics of quality work. However, I was not going to operate under the assumption that my middle school students would know how to write good feedback. I was going to train them.