| it's really quite easy.  there are two ways.  to the left of every thread there is a box/button that shows three things:  no changes to the thread, unread/new posts, and inside that, a red or blue dot that shows that you've somehow contributed to the thread.  
 you can also use the search function and simply search for all posts by a particular person.  enter your own nickname into the "search by user name" field and press enter.   you'll get a happy list of all the threads you've ever posted anything in.
 
				__________________My country is the world, and my religion is to do good.
 - Thomas Paine
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