Not just when doing something non-obvious, but also when not doing something that might normally be expected. “We don’t need to synchronize here because <some

Not just when doing something non-obvious, but also when not doing something that might normally be expected. “We don’t need to synchronize here because <some invariant>” and whatnot. Basically, whenever a casual observer might think there’s a bug, either because you’re doing something unexpected or not doing something expected.