I think this is the most important evidence against it. You could parse Quirrel as saying that Harry being Tom Riddle on the map is a surprise and no a trick, and that he is not commenting on himself being Tom Riddle instead of Baba Yaga.
You could also assume that Quirrel is lying about parseltongue. But yeah, I think that drops the probability a lot.
I think this is the most important evidence against it. You could parse Quirrel as saying that Harry being Tom Riddle on the map is a surprise and no a trick, and that he is not commenting on himself being Tom Riddle instead of Baba Yaga.
You could also assume that Quirrel is lying about parseltongue. But yeah, I think that drops the probability a lot.