I just change the title in a thread in the test track that was imported from the old system and the URL and title shown in the list were changed, so I am not sure why this is not working for you.
I am going to go in and see what happens if I change it for you.
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Well I went in to edit the first post and it showed your updated title already in that post, so I just saved and it still did not update the thread title.
Note to Admin: I do see if I go to "Administrative" and "Edit Thread" that the old thread title is still listed there. I am guessing if I were to change it there, it would update the thread title, but will not until you have a chance to look. Not sure if this is just a new permission thing where regular members can not update the thread title, or if this has something to do with the thread starting on the old system.