In the UK it's "You MUST NOT park on a road at night facing against the direction of the traffic flow unless in a recognised parking space."

Source: https://www.gov.uk/guidance/the-highway-code/waiting-and-par...

It's all to do with visibility. The rear light clusters have reflectors built in to them, the front light clusters do not.

I have driven in the UK for 12 years and genuinely have never heard of that rule (obviously did not study the highway code well enough before the test).

Do people actually pay any attention to it?