I don't understand this either... 10,000+ miles and no problems pulling left or with odd tyre wear.
Well, I say there's no problem with it pulling left... I think I'm right in saying that all cars pull left because of the camber in the road.
I certainly haven't noticed anything untoward, but I do know this - many people moaned about getting perfect wheel alignment on their MX-5s. I found that the car, for whatever reason, was very sensitive to incorrect tyre pressures. If I didn't keep an eye on them to keep them at the right level, the whole car felt wrong.
I might ask the dealer to take a look at the 12k service I guess.