Great post, jml.
My rule is MDM on tracks with walls too close and all off on tracks with decent run offs. I think it's a good idea for most intermediate drivers.
I've been off just twice, both times with MDM off, and both times it was not even close to doing any damage, mostly because I appropriately chose the time and circumstances to test the limits (slower track, no walls and no cars immediately close to me).
MDM does help avoid issues, but when it takes over, corrections are not working as expected, which slows you down at best, and I can see it being dangerous.