Originally Posted by
kmersh
I would add that I am not even sure how UA would know if I bought my friend dinner as way to thank him for his generosity in letting me use some Plus Points, unless I or my friend told them.
Over the years there have been reports of people being asked about their upgrade at the airport and saying "I bought it". That's why there are multiple posts about coaching the recipient to say that it was a gift from a friend/relative. No trade, not barter, no sale.