This problem is definitely not user error! It may just be a tiny glitch in the system. I will continue to look into it and pass it on to tech!
Some of my posts are still being duplicated and I'm being very careful to hit the "post" button only once. :(
I've had tech look at this, and they cannot seem to replicate the problem. They suggested this may be a "conflict" between the site and the kind of operating system you are running.