It always bothered me about Shadowheart how she's all "I have so many secrets but I won't tell you anything". She's acting like a complete amateur, more drawing attention than avoiding it. If she's a secret agent of Shar on a secret mission of such a high caliber she would assume a false identity like a pro and stick with it. Instead, she introduces herself as Shadowheart which sounds exactly like an ominous Sharran alias and has Sharran symbols all over her gear. Why don't we get a Religion check to recognize that? The rule of cool does not apply here, it's just dumb. And they are completely ruining the chance of having a strong reveal scene later. She's the perfect example how having her as an optional "Origin" PC ruins all surprise and powerful storytelling concerning her character. And why ruin it? Does someone actually not want to create their own character in D&D?? Astarion is the same. Loadscreen art and in-game description just bluntly reveals everything Tav wouldn't know. But even the "Origin excuse" is not good enough for Shadowheart's senseless behavior.
If she's trying to get away with a stolen artifact as the sole survivor of her task force, she should first ditch all the obvious Sharran gear and call herself Karen from Baldur's Gate.