If it wasn't for the stamp outline in the upper right corner, there would have been a lot of postcards written upside down

Sure, but it really wouldn’t matter.

I once saw a postcard where the text was written “sideways” like on a regular sheet of paper.

Some people are ungovernable.

There is literally nothing stoping you from doing that anyway.

So, there are these rules of life, and no one tells you about them, but you get some clues…