The way that UA prints boarding passes is really odd. They always insist on printing the title "MR" at the end of whatever name they have. For me, this ends up with Lastname FirstnameAMR (the A is my middle initial). I called once to see why it only was that way on MP reservations and got a similar runaround as the OP. Now, it shows on all of my BPs. For me, it's never been a problem, just an annoyance.