Well he's at +5 already, but he has it spot on.
When I talk to other programmers who can't see the value (or are lazy) in providing comments, I try to make it clear to them the comments are the RATIONALE for the piece of code. We know we can see a loop that iterates over a list, but why did Fred (who left before I started) write this module in the first place? He could have mentioned in a short blurb at the top that it updates a person's Mojo and that it's only used by the AustinPowers module, thus saving me time doing a global search on the thing. And given that I don't have any RATIONALE for Mojo.dll existing I sure as beans won't have any reference in AustinPowers saying the Mojo was moved into the YeahBaby common library because of some reason or other.
RATIONALE. The WHY of the code, as so neatly put by the op.