Thanks for the response. It seems to see that the rich text / markdown button only makes sense if you have a single panel editor? Otherwise you'd see both at once anyways? In the mockup, I am not sure what switching to "MD" would do. Seems like it is already in MD mode? Either way, seems like maybe those buttons should be next to each other if they affect each other?
FYI, I've been playing around with structuring this mockup in CSS to see how it could be most easily themed. I hope to have something to share this weekend. Not sure if it'll be useful, but seemed better than trying to describe in words. 