Ingrid and Angelia, you guys are silly.
I can just see myself at the next SnB "oh yeah? well I'm so good, my stockinette doesn't curl!"
Knitqueen, this pattern also has a kfb every other row. In the increase sections, it began every row with either kfb or pfb, and now that we're in the straight sections, RS rows begin with 1 purl and end with kfb, and WS rows begin with sl1 and end with p2tog. I wonder what the critical elements are to keep it from curling.
Like with your pullover, there is a part that curls, and that's the very botton part. It curls up like normal stockinette. But the edges don't curl at all. Veeeery interesting.