After entering some documentation in the Ecore Documentation View, the hitting Ctrl + Z or Ctrl+ Shift + Z several times (with either the view, or the metamodel editor in focus), will properly undo/redo changes made to the metamodel.
Sadly, the Ecore Documentation View is not refreshed, so the unsaved state of the documentation can be seen inside. After re-selecting the previously selected element in the metamodel tree view, the proper state of the documentation can be seen.
Undo/Redo commands should update the Ecore Documentation View as well.