Agreed... 5) is minor and just the result of saying "We're not going to bother trying to track if a file goes from having unsaved changes to not as a result of undo/redo - once a file gets marked as having unsaved changes, the only way to 'clear' that is to save the file again."

That option is much better than getting the undo/redo vs unsaved changes tracking wrong and allowing unsaved changes to be easily lost, like notepad does. :-P