They should never tell you the part in your hair looks like a buttcrack.
Yes, I have had a stylist, a curly-specialist stylist, tell me the part in my curls looked lilke a buttcrack. She wasn't exactly the soul of tact.
I actually did go back to her and talked to her about how she really hurt my feelings, so she gets it, I think. She said she did, but I'm not sure she did. She kind of blamed me for not telling her right away that she was being rude
Whatever, I guess it's also our job as clients to tell stylists what good manners are.