If you need 'guidance' in a situation like this then you shouldn't be traveling. I'd have dealt with this the same way the crew member did onboard - I'm not prepared to allow a coat to be in an overhead locker when there is luggage still to be stowed. I think it's fair to say that no person gets 'priority' but certain things may do. Luggage and big bags go up, if there's any space left afterwards then small bags and coats if you really must.