Originally Posted by
canadiancow
I take something like 2A 2E, knowing that either 2B or 2F should have no issue swapping since they're getting an equivalent seat in the same row.
Some people have a great aversion to having the sun shine directly in their eyes or on their laptop screen, and prefer the shaded side of the aircraft.
Your proposed exchange is least likely to succeed shortly after sunrise or before sunset, unless you are giving up the "better" seat.