A Bug in the Messages section
(Do I get the Bug Badge? )
It's almost like the draft saving feature (which is running especially frequently today!!) is posting or trying to post the incomplete message.
This results in multiple messages being posted as well as the initiation of the "spam blocker" feature where you need to wait 60 seconds before posting "again" because you have supposedly posted twice in less than 30 seconds.
Tech support! @HeatherBoyd etc.