This whole topic is really a non-issue for non-Forgotten Realms fans. Most of those players, I imagine, will be like, "Who's Shar?"
And as someone who didn't (and honestly still quite doesn't know) who Shar is it is still a problem.
First of all, we are not playing a fish out of water. Our character is a denizen of the Sword Coast and is likely to have knowledge and opinion on Shar. What player does or doesn't know is less relevant that what our character should and shouldn't know.
On top of that, in spite of what seems like obvious giveaway to those who know the lore, the game at the same time expects players to know who Shar is. Right after revealing her identity to the player the game expects player to state their opinion on the matter. Less jarring now after X number of playthroughs, but it felt realy bad to be asked to react to something that has no meaning to myself.
As I stated before it is one of those issues I would blame origins on - the game will spoil every origin companion during character creation, so one might think it is pointless to keep the pretences up. At the same time, it is narratively weak to just not even try creating believable scenarios to react to.
