When you hit "submit", watch the progress bar in your browser and hit "Stop" in your browser when it has reached just under a quarter full. I noticed this helps to cut the number of duplicates back to one or two as opposed to 3 or 4.
Also, if you are the OP of a thread that has posted multiple times, you can delete the extra threads before they have been replied to. Click to view the thread, and in the top right hand corner of your message will be a grey "X" in a square. This will delete just that one, not all, so it may be that you have to do it 2 or 3 times to get rid of the extra threads.
HTH
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