Why is it that I never seem to create duplicate topics? I have an answer for you.

When you create a topic, the site hangs, for anywhere from ten to sixty seconds. If you hit "enter" during that period, get frustrated, you will make the site continue to lag, but you'll also send another query to create another topic. Thus, the duplicates. Obviously there is something wonky going on someplace, since those dupes can't be posted in, but the simple way to avoid it on the user side is to just wait whenever you post a topic. Don't get frustrated and hammer the enter key. Don't slam your fist on your keyboard in frustration. Just wait for the page to load. I know it sucks, but the vast majority of dupe topics are, in my estimation at least, generated by a combination of user impatience and whatever this code issue is.