I no longer know what I meant with "document string is 
broken".
It is not very clear, but not broken.
It does not specify clearly the return value
in the case of 'without arguments'.

The problem is still present in trunk.
Problem is as far as I understand it:
Some return values from tcl are strings
that may contain spaces (or are even certain to contain 
spaces).
They are nonetheless translated to a Python tuple by
Tcl_SplitList in _tkinter.c.
There is no difference in syntax between tcl lists
and tcl strings (with spaces).
You have to have contextual knowledge to do the right thing.
This knowledge cannot be attached to itemconfigure alone
(for reconstitution of strings) because then information
about whitespace is already lost.
For return values known to be strings _tkinter/TkApp_SplitList
must not be used.

So I think it's a more general bug related to tcl string
return values.
Other Tkinter bugs may have the same explanation.
Don't know how to resolve this without a lot of work.

Matthias.