A first class passenger hung the jacket behind his seat. There are no places in coach to hang a jacket, behind the seat or anywhere else.
Some planes have hanger hooks behind the last row of first class seats in addition to the closet space up front. This is where the jacket was hung - as good a place as any.
Sounds good to me. I would have offered my space as many would do. Folks must understand travel in the friendly skies is much different than 1990.