List why, if you could be so inclined to do so. Providing a link would also be adequate. It doesn't have to be a current thread; hell, it could have been made years ago, just link it. My absolute favorite is this gem. The reason being that it really refined the idea for me that moderators are really people, too. People who have feelings, as well as a sense of humor. One of the things that inspired me to apply, as well (yes I know that's shallow). Post away.
