There are sites that block the public from reading reviews, and I have been subject to scathing criticism by fellow writers on these sites. In the early development stage of my writing, I dreaded opening a review. But those criticisms helped me. I took the negative with the positive. On GA, because the reviews and comments are made available to everyone to read, I would never humiliate a fellow writer by saying things like: Your work sucks. I will, however, PM the writer and tell him where I think the problem lies and suggest a solution.
As an editor, that's entirely another issue. I am harsh. I never say, Please change this, or please delete that or Try to use a different word. I give an instruction. Change this. Delete that. This does not make sense contextually. Word is wrong, use your dictionary. Please buy a dictionary! Rewrite for clarity and precision etc,. I don't have time to dwell on benevolent requests. As a reader, however, I'm different.