When this issue of 'the ground as a make-do neutral' comes up, I think we run into two issues.
The first is the natural outrage of any properly trained sparky. "WE don't do that" and "that can't be right" are proper reactions.
Countering this is are the practices, even necessities, of electronic design. A 'dirty little secret' among the engineers and testing labs is that 'off' doesn't always really mean completely off, and that ground gets used for 'insignificant' amounts of current.
Which, of course, catches us on the horns of a dilemma: do we admit this, or even talk about it?
We have to know about this in order to do our jobs.
Yet, we don't want some uneducated noob to skim over a thread, and walk away thinking 'I just learned a neat new trick - I can't wait to use it - I don't really need that 4th wire to my new range after all!'
Getting back on track of this thread .... sometimes you really need a ground wire back to the panel; a GFCI might address safety concerns, but it will not create a ground path for you.
Perhaps we also need to recognize that nothing lasts forever. For example, my house was built in 1940, using the original version of Romex. That is, no ground wire. Maybe - just maybe - it's unrealistic to expect to continue limping into the 22nd century with an electrical system that is no longer adequate. Maybe there IS a time to knock it down, and start over!
