My wife and I got booted out of our seats both ways this past week. I was booked on Tango Plus, and my wife w/ infant on Tango. On the way there, seat selections on AC 109 from YYZ to YVR on September 7th were changed (24A and 24B were booked as this row only had two seats on the originally scheduled 321 flying). However, the aiircraft was changed to a 320. Got a refund statement for seat selection of $15 + taxes via email, although no explanation was given whatsoever as to why the selection was refunded. Fortunately, there were still 2 seats together open on this sold out flight, and I was able to get them through web check-in.

On the way back, travelling on a 762 on AC 192 on September 9, and reserved 20D and F. Checked three days prior, and we still had those seats reserved. On the morning on the 9th, went downstairs at the Hyatt Vancouver to check-in (they had a check-in machine there), and to my surprise, wife had been moved to 15H, and I was moved back to 34A. Luckily for me, since I was up at 6am (due to time change), 20 DEF were still available and I switched back. No idea why this happened, and I did not receive a refund for my wife's separately paid seat selection. Flight was not close to being sold out, so why we were kicked out, have no idea. I have written to AC to request a refund at least for my wife's Tango seat selection in which we paid $15 for advanced seat selection (I technically want the $15 for my Tango Plus ticket as well given the extra fare is in part due to the privilege of advanced seat selection, but am not pursuing it). Even though we did end up with our original seats, if I hadn't checked in earlier, we would likely have lost them.