I have 2 dds with autism, and we work hard to manage them both and try and make sure they arent shut in the house and have access to everything every hcild their age does. However, some people seem to think its helpful to say "oh you would never know, are they sure?" I mean seriously 
We were at musuem the other day and the teacher there asked what we had been up to, we explained we had been to horse riding therapy and camp with our support group, and turns out she knows some of them. But then proceded to grill me on "how asd effects my girls as they seem normal" 
2 mins later DD2 had a huge meltdown as she couldnt be a cat (dont ask!) and trying to push me down the stairs, hit and screaming at me.
Im not sure why it bothers me so much, but it does. I would never question if someone told me they had an unseen disorder, tbh i think its rude