This policy setting controls whether hidden markup is visible when users open PowerPoint files in standard or HTML format.
If you enable this policy setting, PowerPoint ignores this flag when opening a file, and always displays any markup present in the file. In addition, when saving a file, PowerPoint sets the flag to display markup when the presentation is next opened.
If you disable this policy setting, PowerPoint sets the flag according to the state of the "Show Markup" option on the Review tab of the Ribbon when it saves presentations in standard or HTML format. In addition, PowerPoint enables or disables the "Show Markup" option according to the way the flag is set when it opens files, which means that a presentation saved with hidden markup is opened with the markup still hidden.
If you disable this policy setting, the behavior is the equivalent of Enabled.