Slavery on Roshar has been shown to exist in many different forms.
Selling a woman of high dahn ... would be a risky gambit for a slaver. Most owners in civilized lands would require documentation of the slave's past, and it was rare indeed that a lighteyes was made a slave, aside from ardents. Usually someone of higher breeding would simply be executed instead. Slavery was a mercy for the lower classes.
One cannot hide as a slave; the brand(s) on a slave's forehead would always give him/her away.
- Shen (previously)