Well, given that the alternative ebrownv was considering was ongoing tinkering during runtime by a superintelligence, it's not quite clear what my ability to build such code has to do with anything.

There's also a big difference, even for a superintelligence, between building a systematically deluded observer, building a systematically deluded high-precision observer, and building a guaranteed systematically deluded high-precision observer. I'm not sure more than the former is needed for the scenario ebrownv had in mind.

Sure, it might notice something weird one in a million times, but one can probably count on social forces to prevent such anomalous perceptions from being taken too seriously, especially if one patches the simulation promptly on the rare occasions when it doesn't.