Puffin I don't think that comment is necessarily about behaviour/quirks (of course you know the context and maybe in that case it was). I know I have had very similar conversations with the (very limited) friends we have discussed miss HG+'s IQ with - I clearly recall standing there watching all of our kids scrabble around in the playground and my friend saying "I don't know how to say this, but she seems perfectly normal to me", she wasn't implying that my kid should seem weirder, just that she couldn't see any real differences. She was not being snippy or rude at all, just stating the truth - my HG+ child is not one that stands out like a sore thumb in a playground, particularly when playing with the bright to gifted children of our friends. Particularly at the age she was when we had that chat (4.5yrs old). Do I avoid ever mentioning the speed at which my child is learning academics compared to this friend's same age child? I do. Can you see the difference between the two of them in the playground, not really.
The superficial knowledge we have of other people's kids means, depending on personality, that some high IQ kids do seem perfectly normal to other parents...