Interesting story where the veils necessary to survive outdoor without harm also necessitate another way to identify each other.
it seems like there are scarce resources in this environment and so the requirements to become a named citizen are to give a structured way to handle that competition instead of allowing everyone to be protected from the sun and then have to fight or starve.
My take on Scentless is that Scentless was not actually drowned. She was almost drowned and left for dead by her twin, and returned to find her twin had taken over her home and with it all of her perfumes that mark her as a citizen. So she is left homeless and without identity. I don't know where she got the currency to pay for the expensive scent, perhaps thievery or some trickery involving her weird ambiguous identity or maybe she was filthy rich before and happened to have that much cash on her person before her attempted murder. In any case, she wants to commission the scent of the sea as a part of a plan to get revenge on her sister--I'm guessing she has plans to murder, but maybe she just wants to scare a confession out of her sister or scare her sister into fleeing, but she wants her sister to know who has come for her and to probably think she is being killed by a revenant. Scent is the most evocative of the senses, and a society that uses it as a marker of identity would no doubt only emphasize that fact. Murdering her sister in the sea, I imagine that the scent of the sea evokes the memory of that murder very strongly, and so if a strange assailant smelling of the sea attacks her it would bring to mind the sister-murder foremost to her mind.