The captain had several of us change our seats, spreading us out more evenly to better balance the plane.
Flying in Bulgaria relatively empty planes our seating was always rearranged.
Only pilots and aviation engineers seem to know that a plane has to be balanced fore-and-aft or it can become uncontrollable.
A stable plane is a happy plane. Constantly trimming and pumping fuel to correct for balance is ‘No Bueno’. As one early instructor said “You’re driving a plane, not a roller-coaster”.