Hmm... where to start with insults...
One of my close friends never actually said it, but she's implied a few times that she doesn't like my curls and she's glad that she doesn't have hair like mine. Once she was like "Your hair is so poofy, Lexi!" If she ever does that again, I'm gonna say "I would rather have poofy hair than flat hair."
Sometimes people on IM are like "You have really poofy hair that needs to be straightened." Mentally I'm like "Why aren't you saying this to me IN PERSON?"
I've also gotten the "You would look pretty if you straightened your hair" from a few people. Also, during spring break for the French trip to Quebec, a girl said that she could try straightening my hair. Then again, I've also gotten "You would look weird with straight hair" from a few people, which I'm not sure to take as a compliment or an insult.