Remember what your mother told you about saying ugly things about other people?

It didn’t apply in the case of Hilary Mantel, British author of the blockbusters “Wolf Hall” and “Bringing up the Bodies.”

What is supposed to happen is that, in saying unkind things about someone else, you harm your own reputation.

What happened when Ms. Mantel made some pretty barbed comments about the Duchess of Cambridge? Her book sales increased dramatically.

Judging from published responses, people don’t agree that Kate Middleton appears “designed by committee and built by craftsmen, with a perfect plastic smile and the spindle of her limbs hand-turned and gloss-varnished.”

Perhaps they rushed out to buy Ms. Mantel’s books just to see what else they might disagree with her about.

Ms. Mantel, after all, didn’t make her injudicious remarks during a yuk session. She was giving a lecture about the monarchy.

Some suggest that her remarks were taken out of context, but Prime Minister David Cameron was disappointed enough to say, “What she said about Kate Middleton is completely misguided, and completely wrong.”

We wonder if Hilary Mantel’s mother might have stuck to her motherly guns. Or might she have enjoyed seeing “Wolf Hall” and “Bringing up the Bodies” climbing the charts?