Hidden comments
From Code Snippets Wiki
A hidden comment is an HTML tag that hides comments with the (<!-- -->)
[edit] How to make a hidden comment
To make hidden comments, simply add the <!-- tag, type what you want to hide, then end it with -->. Hidden comments are used mainly as hidden notices to people editing a page, and is supported by HTML and MediaWiki, meaning, you can use this code in building your website, or on this or any other MediaWiki wiki, including this one.
