...If there are 4 seats, is seat 1 or 4. Then if somebody is in seat 1 you sit in 3 or 4. Same goes for toilet stalls/urinals. That rule has been broken several times with me this week.
And if in an empty car park with a million spaces there is somebody in number 1370, you don't park in number 1371. As somebody did to me the other day.
And in a 4 seat face to face train bit, you sit opposite and along from the person already there. You don't sit next to them.
Please learn how to sit people!