When you get Shadowheart to confess that she worships Shar and talk to her about Shar at camp after that, you can pick the dialogue choice towards the end that says, "I'd be lying if I said it didn't sound convincing. You should tell me more some time". Three people will react to that. Shadowheart approves. Lae'zel disapproves (no surprise there). And Astarion approves.
I don't know if it means anything to see Astarion showing approval for the main character saying she wants to learn more about Shar. But he could be the other Shar worshipper that the game has spoiled for us.
