Quote Originally Posted by Kareeah_Indaga View Post
Durnehviir seems to notice on some level (you can call him out on giving you a Dragon name without getting to the point where you yourself find out you’re Dragonborn and his response is "Forgive me, my instinct was to grant you this title. I am uncertain why. Perhaps one day it will become clear to both of us.") and Miraak definitely notices ("What? Who are you to dare set foot here? Ahh... You are Dragonborn. I can feel it. And yet...")

My head-canon on the subject is that your soul gets more noticeable the more Dragon souls you absorb.
Maybe the dragon at the tower just didn't catch on that this is what he felt. "Dragonborn? Nah man, there's no way, I'm probably just imagining things."