0.5.8 windows 10
I was demoting someone so I don't have to provide luxury to them, when at the slaver's guild, it said I could demote further past slave and it would turn into noble. It didn't stop me at any point saying it's not allowed or this could not be completed, and when it did complete in one day, I could turn in a "nobleman is looking for a bride" quest with a Slave demoted to Noble.