Originally Posted by
Hipplewm
SO MUCH THIS - Do NOT tell the GA - it will confuse them and 99.99% chance they will screw it up - they are good at what they do, but you start asking them things out of the ordinary and the wheels will fall off
It's not just "out of the ordinary" to give someone else your upgrade, it's not allowed. From the airline's perspective, you either take the upgrade, or you reject it, in which case the GA upgrades the next passenger on the list. We do not get to assign our place in the upgrade queue to another passenger.
Swapping seats once you are onboard, by contrast, happens all the time and is generally not an issue.