The best comment I ever saw was in a body-corporate-management suite I maintained for a short while.

The comment was at the beginning of a 200 000 line pascal program. It was the only comment in the file.

It advised anyone being approached to maintain it to at least double their quote, as the code used 1 and 2 letter names for variables, constants, functions and procedures. It also advised that the same variables were used for multiple purposes, and that maintaining it was a total nightmare.

The comment was correct. The only variable name that made any sense was l (el, not one), which always held the current line the cursor was on. I was thrilled when I worked out what l (el) did.

-- added clarification due to fonts that make l look like I or 1