The argument is that, if you don't know she's a cleric of Shar, then they look decorative, not suspect.
The counterargument is that if you are from any socially connected part of the Realms, say Baldur's Gate, the black circles don't say "decorative" but rather SCREAM "symbol of Shar."
I say it looks like jewelry and decorations which I might add are clearly worn in "socially connected parts of the Realms.
But you say otherwise. So. Prove it. Prove that people in the Realms don't suffer other people to wear onyx. With or without a purple border, apparently.
I guess they don't use onyx in Baldur's Gate to relieve the pain of childbirth?
I guess the random treasure tables get changed in Baldur's Gate to make sure they don't give out any onyx?
