For me at least, even knowing the that Q=V, and seeing the clues, they don't intrinsically point to that. Most of them can be explained simply by the idea that Quirrell is subtle, evil, and likes corrupting people.

The Law of Conservation of Detail (TV Tropes warning) implies that an important character who is subtle and evil (or even just subtle) has a substantial probability of being the villain.

I hadn't read the original series either, and so at first I had no idea that Q=V except from the Author's Notes; however, I suspect that by this point in the story I would have begun entertaining it seriously as a hypothesis. (And of course as long as the story is still being written, there's always some chance Eliezer could change his mind.)