My guess is one possible aversion is 'have the protagonist be mind-altered so the obvious clues don't add up', which is one of the leading theories for 'why hasn't Harry figured out yet that Quirrel is Voldemort even though people were figuring that out by like ch20?'
Well, part of it is that Quirrel is Voldemort in canon, which is significant evidence that Harry doesn't have.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.