Also, what if someone starts a duplicate thread and everybody who is just logging on goes to the new thread and the old one does not get bumped often enough to stay visible in latest posts? Then someone posts a stupid or misguided opinion which was thoroughly refuted on the original thread. The people who only read the new thread see the opinion but not it's refutation. This is convenient for the person circulating an untruth but not good for the quality of the debate.
Good point.