Omg, I’m still in shock 
These people have just released a rich text in-browser editor (demo) that does exactly what I was trying to do with Shift Edit. They even took the same route with their Javascript and implementation. I’m totally psyched that they could build it out so well (they can undo, select text…basically all the stuff I was having trouble doing), but damn…I’m so bummed 
UPDATE (1 hour later): I’m still ticked off but they don’t have versioning in their framework or shortcut keys yet. A small victory for Shift Edit 
Rich text (WYSIWYG) editing on the web is a difficult problem. Browser-based rich text editors to date have failed to meet users stability expectations or in other ways subtly break the seamlessness of the editing experience. The Dojo Editor widget, written by Paul Sowden and David Schontzler, provides a solution to these problems in an easy-to-integrate package.