It's intent. I went to a boarding school, kids lived in 'houses' with housemasters. They were pretty good, not as dickensian as it sounds.

Depending on the housemaster, and provided you didn't make a habit of it you could call them wankers or more, occasionally get away with calling them a cunt. All relaxed.

But if you intended to offend then far lighter swear words would be taken much more seriously. You could get into trouble just for using the word 'bloody' if it was not meant in jest. Odd, but it worked in my view.