Originally Posted by Carl V
I hope they improved the code since 1981
NO and the poor connection from the receptacle to the branch circuit conductors often causes the plug to burn off and since trailers use a lot of wood paneling the wall get scorched or starts on fire. The trailer industry uses this wiring method because it is cheap , saves time and is often not subject to 3rd party inspections.
When they allowed the use of aluminum Romex we were constantly replacing burned up wiring in mobile homes.
There is a huge difference between meeting the code and best practice. We never back wired receptacles not because it wasn't up to code but because it was a source of problems for the home owner and led to warranty issues down the road.
On Multi wire circuits you cannot use the device to splice the neutrals or the neutral connection can not be dependent on the device. A bad neutral in many cases is more dangerous than a bad hot . If you lose the neutral you could end up with 240 VAC
impressed across the load.