Yes, I'm with Arria here, there's no rules that were handed down by the Gods. In French tu used to be very exclusive, only between close friends - even within the family kids would be expected to address their parents by vous, and ceratinly at school it was the overall word, but that's kind of changed in the last forty-fifty years - some places at least.

Swedish has few honorific modes of address, and there's a lack of words that would feel useful for titles if you want it formal in a D/s relationship. To use slyna/slampa (slut), slav (slave), hora/luder (whore), mästare (Master) or härskarinna (ruling woman/Domme) in front of the name would come out stilted like hell or even tasteless. The English words Sir, Mistress, Master and the like sound much more useful for titles.