A MOD can delete duplicates within 24 hours, but the 15 minute thing, there might be a "cancel post" feature, not sure, but what I have done with my own posts in 15 minutes or less is open it, then highlight the entire post and press backspace on the keyboard.
This will wipe out the text but your alias still shows and it counts towards the 15 per day freebee membership.
I'd not worry about dupes on this board...no biggy.
Hope this helps.
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