It's possible that they thought the first one didn't post and kept trying. Sometimes you get a timeout error and return to the editable text with the post button again but the post already went through.

It’s a common bug that the post button on some interfaces doesn’t seem to do what it should when it actually does but the interface doesn’t show it.

Sure, fucko. I pressed submit and the site brought me back to the same page, so i thought it didn't go through. How old are you? Have you never seen this happen on the internet? It's due to the platform being new and not having anything to prevent this behaviour.