Following on from T175634, there is still an issue with browsers which don't support InputEvents (e.g. Firefox, Chrome<60, probably IE).
0. In Firefox
- Enter two lines of text
- Move your cursor back to the first line, and right-click -> undo
- Observe that your second line has been modified in the view, but not the model.
This happens because we only observe the node containing the selection for changes. In this case the first line is selected, but the action modifies the second line