Oversighters have the ability to permanently hide revisions from view. This is often used to hide personally identifiable information that was posted inappropriately. Oversight is also sometimes used to hide particularly harsh libel or personal attacks. It can also be used to hide automated vandalism edits by vandalbots made with the intention of hindering the usability of Conservapedia.
Revisions hidden via oversight can only be restored by a developer.
For more information on this feature, please see the MediaWiki release notes located at http://www.mediawiki.org/wiki/Extension:Oversight.