Codifying all expected social norms among an arbitrarily diverse group of people in a concise but fully understandable form is impossible. Attempts to do so just leave loopholes, edge cases and personal interpretations the size of jumbo jets which will be abused. This doesn't try to do so and leaves it up to you to observe the social norms of the group. Like has been done by humans since the dawn of our species.
edit: A false sense of security if not actually security as the author of this article found out.
You don't need to codify all expected social norms because the CoC is applied by and for people, who can extrapolate to fill the gaps. You do need to give them a starting point, and since there is no obvious universal definition of "don't be a dickhead", you probably want to list some concrete examples.
If people are idiots about enforcing the CoC, I'm willing to bet they'd have been idiots about enforcing the "don't be a dickhead" rule too.
edit: A false sense of security if not actually security as the author of this article found out.