Peer feedback is more powerful than teacher feedback
Why? Because students hear it from a peer they relate to, not an authority figure. And giving feedback makes the giver a better learner — they have to think critically about what works and why.
But peer feedback only works if you teach students how to do it. Left to their own devices, they either sugar-coat ("It's good!") or tear down ("That's rubbish"). You have to build the culture.