What is post revision?
Admin can specify whether to enable post revision for each forum. If post revision is enabled, every message being edited will have “Revision: 1” link showing at the lower right of the post. When a message is edited, the previous version will be stored and available for viewing. This is a very flexible feature because Admin/Moderators can decide whether or not a message should be revised when they edit a message, thus overriding the default setting in the admin panel.