> Comments are not documentation.
Probably overly generalized to be pithy, but no.
Comments are by very definition documentation, which can and should cover of all of the what/why/who/how/where.
Documentation that occasionally explains how to use code can actually be useful!
Unless you actually get around to writing a user manual (which gets out of date), please do consider documenting how something should be used, particularly in libraries.
As a Perl developer i mean this literally and transfer it to other languages as well. POD (or a block comment above a function) describes the API and use cases of the function. Inline comments inside the function exist only to provide explanation for the next maintainer when they see a strange construct. Any other type of comment needs to be refactored.
Also, i never said documentation isn't useful. HOW and WHY are useful. WHAT in documentation and comments isn't because it should be in the variable/function/method/class/instance name.
(Who/Where/When are covered by the source repository and the blame function.)
Documentation explains HOW to use a thing. Good comments explain WHY a thing is strange. Bad comments explain WHAT a thing does and must be made redundant by extracting and naming the thing.