I know this is going to sound petty, but if the coat was in a suit bag then technically it is a carry-on and therefore is not allowed to be hung on the coat hooks behind the last row of seats. The FAA is very strict with us as far as approved carry-on bag stowage and right now those hooks aren't an approved area. If you had removed the coat from the bag and hung it on one of the provided hangers then you probably would have been fine.
Technically the f/a was correct in not hanging the bag there, but it would have been nice if they had explained the reason.
Sorry you didn't get a PDB, was boarding on time or was the flight running late? What type of airbus were you flying? It's a pain when you taxi out and then sit for so long waiting for take-off, but after you leave the gate the f/a's are only allowed to perform safety related duties while the airplane is on an active taxiway and unfortunately serving drinks doesn't fall into that category.
Hope that answers your questions.