One disturbing thing about the Petrov issue that I don't think anyone mentioned last time, is that by praising nuclear non-retaliators we could be making future nuclear attacks more likely by undermining MAD.

Petrov isn't praised for being a non-retaliator. He's praised for doing good probable inference -- specifically, for recognizing that the detection of only 5 missiles pointed to malfunction, not to a U.S. first strike, and that a "retaliatory" strike would initiate a nuclear war. I'd bet counterfactually that Petrov would have retaliated if the malfunction had caused the spurious detection of a U.S. first strike with the expected hundreds of missiles.