>Won't just editing a post over and over keep the thread at the top? That way, the thread doesn't have to keep
getting longer.

I think that posts keep their original date (and position) no matter when edited, but. I also think that jo has added to the thread and then immediately deleted the new post, which removes any trace but has the effect of moving it back to the top (briefly ;). [whoever added the last post could try this and confirm.]