Recently, I've come across these articles:

1. A concise one, concerning more the PR author side:

https://slack.engineering/on-empathy-pull-requests-979e4257d158

2. An elaborate one, concerning more the PR reviewer side:

https://mtlynch.io/human-code-reviews-1/
https://mtlynch.io/human-code-reviews-2/

I wonder if it is worth to find a place for referencing them in the CONTRIBUTING.md and COLLABORATOR_GUIDE.md respectively (or in some other more appropriate doc).

P.S. A new one: https://css-tricks.com/code-review-etiquette/