Quality over quantity – The right way to comment your code

You've neglected to mention the most harmful possible comment: the one that is wrong, especially when it was once correct, but wasn't updated in concert with changed code.

Also, I must admit that I have (as I surmise many of us have), as you say, read "a code file that was loaded with comments, but when you actually read them, they were largely useless" and then realized that it was my own authorship!