Yes Nako, (and others asking); one of the horses is dead but there's always more to agrevate...
The debit card is like cash in these purchasing instances and thus, the store has already been (instantly) paid. So when you do a return, if they have to put it somewhere, they offer to put cash in your hands. It is what you gave them, after all. Tell the sales clerk you eraned FF miles for it and they will look at you as if you have three heads because many there have no care for miles anyway, I find.
If there is an issue, it would be the policies of banks and stores. Even if we all decided to be ethically perfect 101% in everything we ever do in our entire lives and we all WANTED these miles to be put back on the card when returning our items, I do not know how we or the banks would let this occur. The only solution (to appease the self-righteous ones) would be if someone in here were to tell banks with miles-earning debit cards to no longer offer miles on those debit cards. I am not going to be this person as I happen to enjoy my bank card's added benefit. Does anyone else? Good.
Now, I may not purposely go lugging hundreds of tiles back into HD (although this might add to some of my weight training also necessary when you train for marathons to and from Athens or in other cities) but such return-actions could in fact work and I merely pointed this out in here. I had to almost 'fight' about my findings in here though, and THAT is the only reason why much of this thread about it all still goes on today.
Now, with that one more or less solved, consider this (to further agrevate some):
As for the college-enroll thing (miles or no), I find that some ski areas give you the seasons pass for up to 1/3 less if you are a student. Some people I've known have enrolled in school to 'be a student' at the time they purchase this seasonal ski pass (which can be a savings of over $700) and then they unenroll days later. Technically speaking (all ethics aside) they WERE in fact students and that is what the ski area knows as well. You may get less miles when ordering your pass but who cares in this case? Go tell most post college grads who pull in $19k/year (like Joe Millionare supposedly does) to NOT consider this kind of thing...

MM is having fun but is also prepared to run from the police! (ha ha -- only kidding.)