I wanted to know, if there is any moment in Dawnguard that the titular character is acknowleged for his achievements. Are the new Dawnguard npc's reacting to your status as Alduin's bane? Archmage? Harbringer? Anything?

I heard that Durnehviir calls you by name (that is Dovahkiin) but are there any more of this type of interactions?

No he doesn't. He calls you some name that starts with a Q and means Vanquisher. I haven't met anyone who recognizes me as anything other than a Dawnguard.

He also calls you by Dovahkiin if youve killed Alduin.

That is lame. I thought that there would be a line for example like this one:
Harkon: You want to destroy me? A mortal, huh!
Dovahkiin: You really do not know who you are messing with.

Well not exactly these lines.,but You get the big picture.

Actually, I think he calls you that after kill Mirmulnir. He still addresses you as Vanquisher no matter what, but comments that he isn't sure why he views you as a fellow Dov.

If you killed Alduin, he says anyone who can kill the World Eater is a fellow Dovah, and that the news of the Dovahkiin has even reached soul cairn. *Celeb*