++ for the excellent node. I frequently find comments that violate the DRY principle. They just repeat the code. They cause the same maintenance problems that repetitive code creates, often worse since some developers read the comments more carefully than the code.
I liked the comment on mathematicians, physicists, etc. avoiding textual descriptions of theorems and designs. I suppose testing is a good way to help us understand both code and theorems (even when they're well written).