Just would like to share my experience: I successfully integrated Q2A with Wordpress. Then, however, I couldn't manage to log out from WP on Safari. There was no error message, the user just kept on being logged in.
I solved the problem by changing in wp-config.php
(without the dot)
Note that my main Wordpress installation is located at mysite.com and Q2A at support.mysite.com. I don't use any subdomain with www.