^ I think the anti flood-posting would disallow that - IIRC you're forced to wait 10 seconds between posts. The other duplicated posts were a minute or so apart.
This seems more likely to be a "It doesn't seem to have worked so I'll try again" error, because it may not be immediately obvious how to view a freshly-posted message.
OP, try clicking on the "Click Here to view your message" link which is displayed immediately after you've clicked the "submit" button.
That will force a redisplay of the page you've posted to - which should now include your post as the first item displayed.
I've seen posting errors which result in no post being submitted - but never a "silent" one: the post failure is always trapped and clearly reported as a failure.
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Giraffe: a ruminant with a view.