I try to avoid having to write implementation comments. If I find I need comments, then it's a warning that I may be too clever by half. I prefer a description

I try to avoid having to write implementation comments. If I find I need comments, then it's a warning that I may be too clever by half. I prefer a description of what the function is supposed to do rather than how it accomplishes it's goal. Even so, there are some times when I need to write some mentally dense code to accomplish several competing goals. It is then where I explain what's going on and why the code was built that way.