Not to put anyone down, but where are these questions (and some of our posters) coming from?
Sounds like a little Southern back-handed courtesy at work, much like "bless her heart:"
Old lady-That little girl has a face only a mother could love. Bless her little heart.
Southern woman-Your mother is a Briles who sleeps around. Bless your heart.
Wife- Honey, do these jeans make me look fat?
Husband- Bless your heart, dear, but you've been a whale for the last ten years and I still can hardly believe you haven't imploded into a black hole due to the force of your gravity yet, so no matter what you wear, you'll still be a walking pork rind.