Good feedback is pokey

And bad feedback is smooth.

Good feedback has sharp specifics. Bad feedback has rounded generalities.

Good feedback focuses on the actions. Bad feedback focuses on the person.

Good feedback has clear pointy spots to round off. Bad feedback has no obvious areas of focus.

Good feedback is a pineapple: pokey on the outside but worthwhile underneath. Bad feedback is a lemon: smooth on the outside and sour underneath.