It seems that you already got a solution for your problem. How did you solve it?
It was a bit odd in my case because the Mojo Marketplace plugin was pre-installed but did not appear in the overview wordpress control panel.
I also thought that I did not installed that plugin but then I noticed in the css plugin editor that it was indeed active and somehow it was also not visible in the regular plugin list. You have to check the separated plugin overview of your mainhost account (Bluehost in my case). I found that crucial plugin there and could deactivate it – and now the commentary system works fine.
