The dumbest comment I've gotten was from a girl my sister used to hang out with. On a day I happened to straighten my hair this is what she said to her friend whom I had just met:
"See how straight and smooth and flat and pretty her hair looks today? Yeah, it doesn't always look like that."
Me: "WTH?!"

Some of my other favorites include:
Straight haired ladies asking me to teach them how to make their hair curl like mine. ("would like a copy of my DNA?")

A friend of my moms consistently tells me "I want to stick my hands in your hair and just shake it around!" ("he he, yeah, no. ")

Girls telling me "oh, I have curly hair like yours but, I straighten mine" as if for some reason that's preferable in most social situations.