This happened on United, but I'm thinking it might be more appropriate here since it perhaps could apply on any airline. Last night we were in an E+ exit row, so I could see the front of the bus. The GA had announced that F was full, but after boarding she approached a man in an E+ window seat and said he had been upgraded. His row (like most E+ on that flight) had the middle open.

He walked to the F curtain, took one look, shook his head in a very obvious decline and returned to his original seat. I wasn't close enough to hear the reason but was struck with curiosity. I'm not all that impressed with F on A320s anyway, but since this was a coast-to-coast overnighter it might have offered a little more comfort.

Any ideas on why someone might decline? Just seemed weird to me.