There is a lack of consistency with it being on the left in Quick Reply, while the full editor has it on the right.
Move one of them, at least. Adding color to Submit to give it visual weight will help too.
Windows users want it on the left because that is how the buttons are arranged in Windows dialogs, but Mac users want it on the right for the same reason. Good UX design for the web has Submit on the right separated from secondary actions like 'Save Draft', 'Cancel' and 'Preview'. Making 'Submit' a different color attracts the eye a bit to help when eyes are scanning for action points.
i.e.
[Save Draft] [Preview] [Submit]