I know I know, Documentation is a bad bad word, especially for us creative people. The true creativity is in writing code, not in writing comments, isn’t it?
Well, regardless, you might find yourself in the situation that you want other people to reuse your code. Or better yet, a different self of you in a year should be able to understand your line of reasoning of today. If you do programming for a longer time you will pass the phase of being shocked at how bad your code was and then get into the phase of having no idea what you where thinking. So a liberal sprinkling of comments can help you get up to speed on your old code.
I invented a technique of chewing on a portion of a programming puzzle where you comment almost every line of code as if you were to explain to somebody the steps in your ingenious approach. Maybe somebody else coined a term for this, for me it helps me sort my thoughts. And probably will do the same a year or ten from now. So commenting comes naturally to me, Documentation by Comment-ation is a logical extension to the concept.