The Anonymous Coward is the default username for editing this wiki, assigned by the software. So if somebody edits the wiki without signing in, then their edits will be attributed to the Anonymous Coward . A few jokers have changed ‘AnonymousCoward’ to something different but equally anonymous … which is OK too.
However, people who really want to be anonymous should know that every editor's IP address is listed (usually) in the entry’s history (found by clicking history at the bottom of any page).