I am getting old too but as far as I know, we are not talking about the same thing. Your quote talks about double clicking the Send button, and I am talking about having refreshed (or reloaded if you prefer) the page. Not about meriting the same post twice at the same time but after a while.
Although I wouldn't be surprised if you've talked about exactly that elsewhere in some of your many posts.
Double clicking or reloading the page had the same result. It's actually the reason theymos implemented the 60 second delay, but that doesn't stop all cases as you found out.