Not sure if this is addressed elsewhere, but I was in 12B on an ATL to BNA regional (don't remember original CRJ aircraft, but know the exit was roughly in the middle).

I'd checked in at YYZ at a kiosk, confirmed my seats on both legs (exit rows). Flight was delayed a bit out of ATL. When my BP was scanned, I thought for a second it was strange that it didn't give me the exit row beep prompting the question from the GA but I moved on.

When I got to 12B, it was the last row, directly next to the lav without an armrest. Another Medallion exit row flier actually got back off the plane and went to the GA and they did something for him. Since it was such a short flight, and I just wanted to get the hell out of town, I just took the seat. But it stunk, and half the flight I had to hold the lav door closed with my foot.

If they changed to a smaller aircraft at the last minute, wouldn't they honor the single exit row seats and issue the receipt at the gate like when you clear for an upgrade, and put non-Medallions in the back?

I suppose on the bigger plane that was not sold out, they just kept all the original seat assignments and moved ones from the back up to open seats. Some guy who was in Exit Row 7 was originally in row 18 or something like that.