Silly things that I feel vaguely guilty about, Part II

I got back to my flat today, and the hall light was on, even though the light switch on my side of the hall was in the OFF position. Of course all this means is that Marie turned on the hall light this morning using the light switch on her side, as she is perfectly entitled to do. But I wanted to turn the hall light off, so as not to waste energy, since I didn't need the hall light to be on, except that I could not use my switch because if I did then my light switch would go to the ON position even though the hall light would be OFF. So I used Marie's switch instead, and now it's her switch that's wrong, and mine that's right.

This seems selfish, like if I were a truly good flatmate, I wouldn't mess with her switch, and would be content to let her switch be the accurate one. But then mine would be inaccurate. Inaccurate! I hate for my light switch to be inaccurate! Why doesn't anyone ever install light switches that have the capacity to be right at the same time? Why does one of them always have to be mistaken? Why? Why?