when i see a "french" flag drawn with the red on the left and the blue on the right, i instantly know that the people who commissioned it, drew it and put it on the wall are not french. what small things only people from your country would notice and everyone else would think are perfectly fine?

hmm perhaps kindergarten kids might draw the french flag like that but i expect they would be corrected by their teacher.

another example thing is the V sign. if the back of your hand is facing the person you're talking to, that's seen as quite rude in the UK, but almost nowhere else in the world.