Because model is normal (as far as I know) I did not understand that 'continue to write' meant doing so without hitting [Cancel] ;-). I might consider being able to do so a feature *if* the dialog were the only one ever created and if subsequent attempts to close merely shifted focus back to the dialog.

However, after shifting focus back to the edit window without hitting [Cancel] and hitting [X] again, I get a *duplicate* "Save on Close" dialog. This is a bug somewhere. I get this duplication on 2.7.4a1 and 3.4a0 also. Only the last dialog created works to close the window.

On 3.3, after closing the edit window with the last dialog [No], I can duplicate the unexpected Idle exit by selecting any of the 3 choices in the previous dialog. This is a second and more serious bug. I do not see this with 2.7.

When I run 3.3 Idle from the console interpreter with 'import idlelib.idle', the Shell window does not close, mimicking 2.7.
The console displays '''
Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python33\lib\tkinter\__init__.py", line 1475, in __call__
    return self.func(*args)
  File "C:\Python33\lib\idlelib\EditorWindow.py", line 996, in close
    reply = self.maybesave()
  File "C:\Python33\lib\idlelib\EditorWindow.py", line 993, in maybesave
    return self.io.maybesave()
  File "C:\Python33\lib\idlelib\IOBinding.py", line 331, in maybesave
    self.text.focus_set()
AttributeError: 'NoneType' object has no attribute 'focus_set'
'''
Running 2.7 shows the same message. So this AttributeError seems not to be the exception causing Idle 3.3 to quit when run otherwise.