Let me be very clear about this: When someone unsolicitedly points out a typo in your work (especially a published book, but even a column or an article) without also commenting on the content of the work, it’s merely passive/aggressive behavior. Ignore them, they’re playing “gotcha.” There’s seldom anything you can do about a typo ex post facto, and the meaning of your content is almost always still clear. When people say, “I’ve found six typos in your book,” I reply, “No, there are nine, go back.”
One woman who found three typos in a column which I had forgotten to proofread actually said, “I assume you’re ill, is it serious?”
No, but it would be serious if I were forced to talk to you daily. When I told her she was being passive/aggressive in the extreme, she was outraged and told me I reminded her of her ex-husband.
“Why am I not surprised you have an ex-husband?” I asked.