Always curious, I set out to figure this out...
Not as easy as it was but the thread can be closed by editing the original post. Go to "More Options" then you can uncheck the "Open" Thread Status box.
Alternately, or in addition to that, you can click on "Thread Tools" at the top of the page and select "Edit Title". There, you can click on the title prefix and change it to "Sold" or "Traded" or "no longer available".
Not as easy as it was but the thread can be closed by editing the original post. Go to "More Options" then you can uncheck the "Open" Thread Status box.
Alternately, or in addition to that, you can click on "Thread Tools" at the top of the page and select "Edit Title". There, you can click on the title prefix and change it to "Sold" or "Traded" or "no longer available".