I agree with you, canalwheeler. That ill person had no business coming to a social event and spreading microbes. I'm not impressed by the argument that he might not be contagious anymore; there are too many variables.

I rarely get colds. I make it a habit not to touch things that many people touch. For example, I summon elevators by pushing the button with the middle joint of my little finger, a finger we rarely use.

In a restroom, I try to use a paper towel to open the door. A well-designed restroom has a trash bin close enough to the door so that I can open the door while holding the paper towel, hold the door with my foot, then lob the towel into the bin. (This works best in a culture where basketball is part of normal life.) If I can't do that, I use my shirttail to open the door.

Now I have a new habit to work on: digging in my purse for my own pen rather than using community pens.