A proxy can actually be obtained for free and they're used very often.

As a mod you need bookmarked a site like: http://geotool.servehttp.com/

You can enter the IP address and find the locations around the country the user has been posting from. Now, if it's a proxy, the locations will jump all over the place, so most likely it's a previously banned poster if the IP address from yesterday has a location in Germany, and the next day if the IP address shows another country. So, there are patterns to follow, and the mod can observe those to come to his or her conclusion about the user.

Remember, all IP addresses are very senentive materal, and Chris needs to truly trust the person he gives a modship to.