The implication of the next part was that IF there was a different spirit anywhere in harry it would be participating in the conversation. Considering how frank the hat is about Harry’s potential for evil, I don’t think it would have lied in a petty fashion like this.
“In your scar.” Not “in you”, not “in your head”, not “in your brain”.
May as well have said there wasn’t a ghost in your left pinky toe, for as much as “in your scar” rules out anything.
The implication of the next part was that IF there was a different spirit anywhere in harry it would be participating in the conversation. Considering how frank the hat is about Harry’s potential for evil, I don’t think it would have lied in a petty fashion like this.
The It being referred to is the nonexistent entity in his scar. Not any possible entity or intelligence. Like the one in his left earlobe.