Over recent years we've seen the software community debate the usefulness of comments (this article being an example), and rightly so. The main argument is against explanatory comments, i.e. "this code is doing X", as the ideal situation is that the code is written in a way that means it's readable and self-explanatory. The problem with comments like this is that they easily become out of date, as someone makes a quick change to the code without reading and updating the associated comment. You then have the issue of a comment which directly contradicts the code it's meant to be explaining.