Miss Manners...

> How is one to respond to "You look so youthful!" I know the right
> answer of course; it's "Thank you." But, still. It peeves.

Then try adding wistfully, "But I would so much prefer to look wise."

Miss Manners so rules.

http://www.washingtonpost.com/wp-dyn/articles/A58523-2005Mar22.html