I think the problem is more, nobody wanted to hammer down these questions before, because it would mean picking the one true way of interpreting it. I don't have a problem not knowing everything about the world I'm playing in, but I need my character's knowledge to be justified in the knowledge of the people around him, or by their own experience. If nobody recognizes Shar's iconography, it's not well known, if it is well known, explain why it isn't recognized. If there was a war to end the universe recently explain that (or retcon that it didn't happen), and explain why it isn't common knowledge.
There's a point when you first meet Zevlor where you hear about Elturel's Descent, you either have no idea what that means or you pass a history check to recognize it. That tells me, that crazy shit can happen and people the next town over still will not have heard of it.
