The submit button didn’t seem to be working so I kept clicking it repeatedly. Turns out it was just slow and every click resulted in another post. So sorry.
You can go back to any thread that hasn’t had a reply, and you’ll find an “x” somewhere in one of the corners - maybe up at the top right near your username? That’ll allow you to delete each of the duplicates.
That might not work - IIRC you can only delete your most recent post. (The reason is to stop people vandalising old threads by removing pieces of a dialog between different users)
Don’t worry about it, one of the administrators will clean up the mess eventually (but since this is Sunday evening, maybe not right now).
(indeed, you can only delete your most recent post, but if you’re the only participant in the thread you delete all, in reverse chronological order)
Don’t worry, musicplay, you are not the first to whom this happened. I already deleted all the duplicates. And I hope soon someone can help you on your raised issue.