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Something I've been seeing a lot lately is that a question or answer will have a problem. Someone will leave a helpful comment telling the person what's wrong. Great!
The problem arises when two or three more people arrive and say the same thing. Even when done politely, as in the example above, it can make a user feel ganged up on. When not done politely, it quickly becomes toxic.
If this is maybe happening from the review queue, consider checking first to make sure someone hasn't already left a comment. +1 that one.
To be clear, I'm not saying you're an awful person if you've done this. I just think having a single critique rather than a bunch will be a more pleasant experience for a new user and be less likely to scare them away.