I was confirmed into first class at check-in 23 hours prior to departure and selected my seat in the app.

Less than an hour before departure at the airport the app said my seat had changed and I no longer had a seat assignment and the app was prompting me to check in.

The check in counter had no information and said the gate agent owned the flight now.

The gate agent said she had removed me from my seat because “there were people higher than you who wanted to sit together”. I asked if I could be given any choice at all about a seat in the main cabin, as I assumed this meant I had been unconfirmed from first class. She said to wait until boarding to find out.

At this point my name appeared on the waiting list for first class and I still had no seat assignment whatsoever.

The gate changed and boarding started and I had no confirmed seat, so I boarded in Group 1 and sat in the seat on my boarding pass. The gate agent made no comment, I assume this meant my seating was correct.

Another passenger boarded and said I was in their seat. I showed them my board pass and the flight attendant called for the gate agent. Boarding was stopped while the other passenger refused to move aside.

The gate agent came to me and said I was not sitting in my assigned seat and she would call security if I did not immediately leave first class. I asked her where I should sit and she said in my assigned seat, despite the fact I had no assigned seat other than what was on my boarding pass.

The other passenger made several derisive remarks towards me while this was happening but was paid no attention by the crew or gate agent. I was made to stand on the jet bridge while the rest of the aircraft boarded, which was humiliating. The gate agent returned with a ticket for 1F, but made no apology.

I never want to go through this again and I am willing to give up my status to avoid being put in this situation again. I would have happily accepted a seat in the main cabin. Can you please tell me whether this is normal?

EDIT: American's Response, it its entirety

Thank you for contacting American Airlines. We strive to put our customers at the center of everything we do. The details you provided highlight the importance of that focus, and we are sorry to hear things did not go as planned. Please know that we strive to learn from every experience, so we appreciate you taking the time to share your feedback with us. Your input will be shared with our team as we continue towards our goal of providing a world class experience. Thank you again for reaching out to share your experience with us. We hope to better deliver on our high standard of excellence next time we have the opportunity to welcome you aboard.