Take complete control of text formatting options on your blog: Formatting and encoding per post, globally on posts, and globally on comments. Text Co
When installed, this plugin will format text the exact same way that WordPress does by default.
You can define which text formatting engine to use by changing the values in the drop down menu on individual post pages.
Additionally, you can change the defaults on a blog-wide basis by changing the "Posts & Excerpts" options in "Your site Admin page >> Options >> Text Control Config".
Finally, you can set text processing for all comments as well. Set this up in the "Comments" options in "Your site Admin page >> Options >> Text Control Config".