They key, from what I've seen, is to facilitate useful conversation. Keep comments relevant and people will learn. Avoid politicking, while still providing evidence for your case. Typically, show your own work. The best review points clearly towards a better result.
Finally, acknowledge your own limitations as a reviewer. We're all human, to pretend otherwise does yourself and others a massive disservice.
(But what do I know. I've been out of the game for a while now.)
Sort of, yes. People develop confidence and expertise from repeated success at accomplishing things. Success creates confidence creates more success. You have to give people room to get that flywheel spinning for themselves.
This works just as well, and has the benefit of not introducing bugs and security problems: "Thanks! I can merge this if you fix A and B."
BTW - much better to get the flywheel turning in the right direction early. It is very hard to turn a gyro once it starts spinning.
They state that reviews are not only meant to ensure good code, but also good coders. That means mentoring, but also merging the code if it's not perfect. Then, afterwards, when touching the affected part of the code again, cc the original author in a fixup PR. I have first-hand experience with this way of reviewing and I really like it.