Unwritten is the assumption, in some households, that you will flush a closed toilet and leave the lid closed upon exit.
Once I learned the practice, searching for the logic of it followed.
It seems waste matter is aerosolized in the flush process. Invisible drops of raw sewage are deposited on all exposed surfaces.
An imposing Anglo man, over six feet to my five foot nothing, sternly taught me the lesson of close the lid before flushing when I demonstrated my lack of knowledge by violating this toileting rule. I’d also left the top up. I never forgot his instruction. He gave an entirely new meaning to the term ‘anal’.
Visiting a girlfriend of recent acquaintance, I saw a sign posted in her bathroom. It read:
Close the lid before flushing.
Leave the lid down when you exit.
Clear instructions without the intimidation. Priceless.