That hits me like something a teacher tells you in a coding class that turns out to be nonsense when you get to the real world.
In a company I work in, we have "no comments policy" for at least ~10 years now and we are not planning to change that. It's not just theory, we work like this in practice and purpose of each part of code is perfectly understandable just from variable names, file names, namespaces, function names.
Everything comes down to proper function naming. If it wasn't clear what function should return, then it was not named properly.