But instructions are given by superiors, while code reviews (generally) by peers. If someone you don't respect starts barking "Change 'this' to 'that'", would you?

I mean sure, in some cases you can completely disassociate from the human side of code, disregard a comment's name in favor of objective truth or however you want to word it, but in a lot of instances you still have to share the same office with that person.

Yes and no. It depends on the team and the culture. My favorite was when I worked in a team of only senior engineers we would leave comments like 's/this/that/g other than than LGTM'. This was all that was needed, no fluff.

In other teams, a comment like this would have meant a chat with HR. We can't make rules for these things, because people and thus teams are different.