I've encountered a few cars where the arrow points to the wrong side, and it's quite subtle if no one tells you.
Who taught you? I didn't know until my 20s and have met many adults who didn't know.
Nobody ever told me and I drove my first car for a long time, rarely drove other people’s cars, and did not have the kind of lifestyle that either supported or required rental cars.
I found out around age 35, I think. From reading it online. I’ve told a bunch of people who didn’t know.