I wouldn't consider this question authoritatively answered in the other threads.
I have a couple other suggestions too:
1) Craigslist. Offer free flight to your destination. Book F seat in name of other party, switch seats on plane.
2) Book the F seat using your name, but NOT your MP number, and try any of the above. If, worst case, you can't make it work, and assuming you're already plat, just call in and cancel the F seat and redeposit the miles.
Originally Posted by
mherdeg
and their downline flights will all be cancelled. Bad times for them.
Thus the big "make sure it's their final segment" caveat.