A few years ago, I was on a YVR-YYZ red-eye that was booked on 321 and then down-gauged to a 320 at the last minute. I lost my aisle exit row seat on the 321 and the same row on the 320 did not have extra legroom. Exit row seats on the 320 were all full.

The GA said she would block the middle seat for me because it was empty. I saw her do something in the computer and she showed me on the screen that the seat showed blocked with some comments about it being for me.

During the flight, the pax in the window seat wanted her friend to come and sit in the middle seat. I told her that the seat was blocked for me. She did not understand and then complained to the FA. The SD came around with some printouts and said that yes, that seat is also mine