There are many superstitions around cooking like everything else. I always wondered about the stir-in-one-direction advice, which i heard in many contexts (sauces, puddings, risotto, etc etc etc).
I think it's totally unfounded.
PROBABLY the reason this one-direction stirring rumor began is that if you make pudding-like cream (custard cream, creme anglais, etc) you will add unwanted bubbles by changing direction. Some recipes even call for straining such creams through fine sieves, to remove bubbles. I never cared if there were bubbles, but if that's a concern, then that's the only reason i can imagine. I always stir everything however i please (often for pure orneriness) and never had a problem.