I recently flew QF PE, booked on ba.com as a codeshare, and the seat selection system was confusing and inconsistent.

The QF site allowed me to select seats, which I did, but even months out the cabin was showing as almost full and I was stuck with a crappy middle seat. I kept looking to see if a better one had come up, but then the site stopped letting me choose, saying I could only ask for a window/aisle. It retained my original choice though. Then it changed its mind again and I could see the seat plan and choose. And then a few days later I couldn't.

In the end I just turned up 3 hours early and managed to switch to an aisle seat at check in. The cabin was totally full so I guess someone else got stuck with my original seat instead.

Anyway, other than that, big thumbs up to QF PE.