I only wish I could have studied Elves and fanfic! ;) But, yes, I know what you mean. I know that, in my own experience, I tend to have such a wealth of information and ideas about my characters that I cannot possibly share in my stories. But nonetheless, it colors my beliefs about how my characters will behave; readers, though, lack this insight, and so might say, "Well, this seems wholly possible," while I would argue quite vehemently that it is not. But--from their perspective, given the information that they possess--they bring up a valid point.

My chief "experience" with Elves (I wish! :P) comes from the Feanorians. To me, the Feanorians behave like too many humans, responding on emotion rather than trying to find the source of their feelings and search for forgiveness; their first actions, when something doesn't go their way, is often to seek "revenge" and turn to violence. I like these characters for this reason; they seem more real to me and it is easier to relate to them. And so I find Elves, given this, more than possible to write, given how the Feanorians are portrayed.