Has anyone seen/heard of NEMA 5-15R connectors being used in a 230V application?

Doesn't this violate safety regulations governing the connectors?

NEMA 1-15 and 5-15 connectors are sometimes used on 220-240V outside the United States.

It was quite common for imported Japanese hi-fi equipment built in the 1960s/1970s to have 1-15 receptacles fitted on the back for tuner, turntable etc.

My brother has a 220V toaster oven he brought back from the Philippines which has a standard 1-15 molded plug/cord set, so presumably it's quite common over there.

One typical application for these connectors in a 230V setting would be a travel adaptor used by an American visitor to Europe

Like Paul wrote, the 1-15R and/or 5-15R are standard in some 220-240V countries. As the safety regulations are (usually) set at the national level, the standards of NEMA (or for that part IEC) aren't necessarily taken into consideration.