Starson17, thank you again. Your pointers saved me days of frustration. I have dealt with all objections that I am aware of.
I incorporated control of the option into the calibre GUI, on the main configuration page. The environment variable is dead.

The option remains tri-valued, as discussed above.
A patch file is in Kovid's hands for decision whether or not to include the changes into calibre.
FYI: 4 files were changed:
- ebooks/metadata/__init__.py (to implement the option)
- gui2/dialogs/config/__init__.py (to transfer the option values to/from the GUI)
- gui2/dialogs/config/config.ui (the GUI changes)
- utils/config.py (to define the option and its default)
If you are curious (I imagine that no one will be

), the bzr patch file auth_sort_changes-GUI is available at
http://charles.the-haleys.org/calibre/0.6.37/