Please add {{Not a test page}} to the main page and all pages that aren't test pages. Message shown depends on the namespace of the page it's being used on. See documentation or source code for details. Thanks!
Topic on Talk:Main Page
Adding the template to Main Page ends up with text that says the main page is a policy, which it's not. The template seems a little wacky. Since Main Page is protected, why is this needed?
Agreed, I don't think it's needed for the Main Page, but possibly other places could do with a local version?