I'm confused. I tried this on your site and did not get it to work.
(1) I registered on your site.
(2) I created a new thread for testing:
http://forum.t-cove.com/showthread.php?s=&threadid=37
(3) I attempted to reply to my own message, and at the reply screen, I then logged out as "theflow", got the "cookies are cleared" message. But In attempting to go back to where I was, I reached a "you do not have permission" error, asking me for a username & password. This would make sense if your site requires you to be regsitered to post messages.
But my primary intention (among several) is to be able to have a Registered user logout at the "Reply" compose screen, get a confirmation message that "you are now logged out", and a link to "return to where you were" (as well as second link to "return to startpage" or whatever...)
So this functionality can't be tested on your site if your site requires that a user be regsitered in order to post. ... It's great to see some real effort being put into this, and perhaps you have solved it. I just don't know yet.