If it helps our discussion, I just opened another (well-known) Turbo Tax competitor's 2018 software, and they say (I'm claiming Fair Use here): "The student must be you, your spouse, or your dependent at the time you took out the loan."
Based on the replies in this thread, and the "...or your dependent at the time you took out the loan" from above, I'm going with: Student loan interest is deductible to the person paying the interest if 1) the interest payer was legally responsible for the loan, and 2) "legally responsible" is effective the day the loan was actually approved, and not the day the loan was originated.
Btw, as far as I know, originated and approved are two different things, that may or may not occur in the same year (e.g loan originated on 12/15/xx, but not approved until 1/5/xx). Additionally, the co-signer is not legally responsible for a loan application (ie. loan origination) that was never approved.
As far as the "grandmother" scenario, that seems like another circumstance that IRS Pub 970 does not seem to accurately address. Maybe the Intuit tax accountant mavens can take this up with the IRS for final clarification.
My thanks to everyone for their contributions and help. This is an interesting thread and I'll stay subscribed for updates : )
Regards . . .
