Yeh. I gave public, constructive feedback listing all problems and how to fix them three times. Two authors left, one started abusing The Butler to do the work for him. Big sad.
Since then, I only provide feedback to the novels I actively work on as editor.
I disagree. The most important thing about giving feedback is to give actionable things, not being nice. If you say something is bad, don't just say it's bad. Give a reason why it's bad and how you would fix it.