Comments by themselves are not bad. The problem is that we often do not write clear code (because it is hard), so we take a shortcut (use comments) to hide the problem. Later, as the code is updated, commonly nobody updates the comments accordingly. In time, opposed to making the code easier to read, these outdated comments will actually mislead the readers. At the end of the day, what we have is: Some code that is unclear by itself, mixed with some incorrect comments.

Therefore, whenever we see a comment or would like to write one, we should think twice: Can the comment be turned into code, making the code as clear as the comment? You will find that in most of the time the answer is yes. That is, every comment in the code is a good opportunity for us to improve our code.