What I generally say to someone who comments on DS's above-level reading (or whatever) is "Yes, he really enjoys reading." That is usually enough for them, although sometimes they seem to want to probe further, which gets awkward like they're holding up a measuring stick between their kids and mine.

My bigger concern, I guess, is the feeling of DS wanting to show off. I know he's fed on people's praise of his "smartness" for a long time, and I'd love to strengthen his self-esteem and wean him off that dependency. We do praise his effort towards reading books that aren't as easy as falling off a log for him. Maybe that will be enough eventually.

Nice to hear we're not alone. :-)