The world has a lot of different standards for a lot of things, but I have never heard of a place with the default screw thread direction being opposite.
So does each language have a fun mnemonic?
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The odd left-threaded screws are called Linksgewinde in German. Knowing this, you can sort of figure the rest out.
Aren’t left handed threads used when there is torque or rotation that would cause nuts on right handed threads to loosen?
Yes. Bicycle pedals for instance.