I feel compelled to reply here. I am the friend of johna who had this happen. It is not just unaccompanied minors who are the issue here. The minor next to us was with his mother! And BA still seemed to find it unacceptable for a man OR another minor (their term is YP for young person) to sit next to him (across the aisle). The attendants did not, however, say or do anything when we rearranged our seating so that the man was next to the "YP"!