Don’t trust code comments over 30 hours old. Inevitably the comment isn’t updated after code changes, resulting in confusion and bugs. In fact, I wish every IDE (Xcode, Eclipse, etc.) had a feature/plugin that would redact comments whenever code is changed, in order to force comment revision.

Here is how it would work. Given some commented code from a game:

 /* Add a fixed bonus */
 score += 100;

Any change to the code would immediately redact the associated comment with X’s:

 /* XXX X XXXXX XXXXX */
 score += time_left * 2;

Alternatively, it could reduce the comment to an Mad-Libs style fill-in-the-blank exercise:

 /* _verb_ a _adjective_ _noun_ */
 score += time_left * 2;

Either way, the coder would be forced to rewrite the comment to match the new code. This would encourage short comments, or better yet, no comments.