WP-Markdown

This plugin allows you to write posts (of any post type) using the Markdown syntax. The plugin converts the Markdown into HTML prior to saving the post. When editing a post, the plugin converts it back into Markdown syntax.

The plugin also allows you to enable Markdown in comments and bbPress forums. In these instances the plugin adds a toolbar, and preview of the processed Markdown with Prettify syntax highlighter applied (similiar to that used in the Stack Exchange websites such as WordPress Stack Exchange).

WP-Markdown stores the processed HTML, so deactivating the plugin will not affect your posts, comments or bbPress forums.