Whatever you may think, people do see code reviews as conversations, and do take comments personally deep inside, even if they try hard to avoid this in the name of professionalism.

Rather than forcing people to exercise self-discipline while reading, it's nicer to exercise it yourself, and write comments in an impersonal way. Assuming that the reader is as smart as yourself just follows logically from the idea of peer review.

This is what I got from about 10 years of doing code reviews, which sometimes needed to be scathing by nature; to induce the desirable changes you've got to genuinely sound like you're acting in the author's best interests, not just do so.