Comment by Mofpofjis

> Understanding code takes more effort than writing it

yes!

> somehow

not difficult to explain. Coding is a creative activity where you work top-down; you decompose the abstract/high-level into the detailed/low-level. You dictate the "events" happening to the code, you are in control. Reviewing is reactive; the code you review dictates what happens in your brain (you are under control, not in control), and you need to work bottom-up: you try to re-compose the whole from the fragments. Even for human coders, a detailed commit message is a pre-requisite before their code can undergo review. The reviewer is in the worse position, so he needs to be supported as much as possible.