I've been testing Schema microdata mark-up in a WP site, and there are some very bad problems --not the least of which is: it won't work.
As far as I can see, you can use the HTML Editor to insert the correct mark-up and Google's Rich Snippets Test Tool will read it. But, as soon as you come out of the HTML Editor to the Visual Editor, the next "Save" or WP "Autosave" wipes out all the mark-up.
I've tried wraping the mark-up in "<code>," "<pre>," and "<![CDATA[" tags, but none will work correctly.
I also tried all the plugins that disable WP Auto Formatting, still no help.