A feature of WordPerfect wherein at the stroke of the Alt-F3 key combination, the document is displayed in a panel as a text document with visible markup, markup which is editable. Turning on "Reveal Codes" makes finding and correcting tricky formatting problems in WordPerfect a breeze (at least for those who know how to use the feature).
WordPerfect's editor makes sure that the markup remains well-formed: if you insert a "start underline" tag it also inserts an "end underline" tag. Deleting one deletes the other as well.
One man's feature is another man's bug. You have to turn on "Reveal Code" to find and correct tricky formatting problems in WordPerfect.