When one reviews another person's PR, it's as if you are reviewing your own. This is not a mere superficial verbiage; a few times, I'll review someone else's code, and actually block on small modifications and comment on them asking for more details, only to discover that the small change was to something I myself wrote and I forgot it so deeply as for it to appear entirely new. As one is kind to oneself often, one needs to be kind to the others, and trust them. It starts from there, and you co-learn and re-learn (which I think is a subtle point in the article), since whether you wrote it or them, it does not matter.