I rejoiced too soon. This evening, clicking on the "go to last post" button of the "Trick It" thread, it took me to post16189995 - a post from April 9th.

I went to another machine and clicked the same button and it took me to post16318698 - which was indeed the first new post for me.

Both machines are running Windows 7 Professional with IE9. They are at different locations on different networks.

Now, so long as I didn't click the "Mark this forum read" option, closing and returning to the thread in fresh browsers consistently returned me to the same two posts on the two machines (the April post on the one machine and the first new post on the other machine).