Allows you to compose content in Markdown on a per-item basis. The markdown version is stored separately, so you can deactivate this plugin any time.
Please refer to this resource: [http://michelf.com/projects/php-markdown/extra/](PHP Markdown Extra).
Your post will no longer be interpreted as Markdown, and you may have to alter the post to remove Markdown formatting.
Just deactivate it. The Markdown version is stored separately, so without the plugin, you'll just revert to editing the HTML version.