On a semi-related note, one of the interesting parts of the Xanadu rule set was this:<p><i></i>Permission to link to a document is explicitly granted by the act of publication.<i></i>
Another example of this is the Python 2 to Python 3 transition. Python 3 is just too radical a change. Many features from it were backported to 2.7 to make the transition easier.
The Xanadu versus HTML choice is more complicated than the number of innovations. The Xanadu vision made you buy into the authors POV whereas HTML didn't.