I admit that I'm a terrible (descriptive) code commenter and that is after 25+ years as a professional programmer, BUT I always try to add a comment when I add some weird code to fix an odd bug or add some special case.

And I can confidently say that pretty much every descriptive comment I've ever written was out-of-date shortly after it was written, but the "hey, this weird because of X and if you think you are going to optimize or fix something you need to be aware of this special case" have saved me numerous times.