Basically, these moms have hit the nail on the head. We have been parenting a "secretly disabled" child for just under a year now. She is cute, cuddly, beautiful, sweet and, not so obviously, disabled. You cannot see the dozen scars on her head or the two shunt bumps and tubing. Her central line is hidden by her shirt as are all of the scars on her chest and abdomen. You can't see the scars on her neck because of her super-cute, chubby chins. You can't tell that her left arm and hand don't work. You can't tell she has Cerebral Palsy. You can't tell that she has Epilepsy and significant neurlogic damage. Her nystagmus causes her eyes to be in constant motion which outsiders take as her "looking around at everything."
My desire to write this post was driven by my sheer need to just get it off my chest. However, hopefully there's a little bit of education here, also. Hopefully when you're out and about you'll remember that people are so very diverse. Everyone is dealing with something. Don't make assumptions and if you have a legitimate question - ask it!