[lmm]

> * refactoring <--- I agree, but refactoring and documentation cannot be mutual exclusive. That's wrong.

Commenting is in tension with refactoring, because nothing enforces that comments remain correct when code is refactored, so they tend to go wrong.

> Use comments wisely, but don't avoid them! Adding 10 extra lines of comments to the file is better than a one-liner no one can understand.

But worse than a one-liner everyone can understand. I think Joel has the right of it: write comments as a last resort when you can't make the code readable enough without them. But don't use them as a crutch to avoid fixing the code.