I have found that there are a couple causes to the duplicate post problem. One is because of the hesitation when clicking the "Post" icon, then clicking it again thinking nothing happened the first time.
Another is caused when you make a mistake, and rather than clicking the "Edit" icon at the bottom of that post, people will click the back button on their browser instead. When you do that the original has posted and when you do what you might think is an edit, you're actually posting another copy.
If you have problems posting, first allow it time to post after you have clicked "Post". If you notice a mistake don't click the back button on your browser, use the "Edit" Function. It should be the icon second from the right next to the Reply icon.
Then if all else fails contact one of the moderators, but lead us to the post in question rather than having us take a guess at which you're referring to. Tell us which section it is in and what the title of the post is. Or post the link to said post.
Thank You
Have A Nice _________