The final, definitive answer

Okay,  it took years of revisiting Blade Runner,  but I understand why Scott said if you don't get it,  you're a moron.   The Final cut was to finally put this to rest,  long before 2049 was announced.   

Deckard not only is a replicant,  he always knew he was a replicant.   Here's why.   

1. When Brian called Deckard in to hunt the replicants, Deckard wanted to decline.   Brian responded, "look,  if you're not a cop,  you're just one of the little people. "  This was not to imply he was just a lowly citizen.   It was to imply,  that if deckard wasn't a cop,  he was just another replicant, and would be retired.   Deckard stated he had no choice,  and Brian confirmed the fact. 

2. Deckard showed an unusual amount of sympathy towards the first replicant he killed in the film,  and the same with Roy.   In a world where the majority of people see replicants as nothing more than products,  you'd think a Blade Runner would not have any issues retiring them.

3. Replicants are amazingly strong.   Strong enough to rip humans apart.   Deckard takes a tremendous amount of hits and damage from these replicants,  and keeps on trucking.   Pris even seems to display some surprise at this,  more than likely because he did not crumble from her initial attempts to break his neck and rip his head off from the nostrils.   Watch again. 

4. The smoking gun is the origami unicorn.  Deckard didn't act surprised at finding the unicorn.   He smiled,  and nodded.   This was more than likely a silent thank you,  for the fact that Gaff understood his kinship to Rachel.   Deckard had an unusual shrine of photos,  memories he once thought were his,  but over time has realized were all false.   Deckard was originally very cold towards Rachel at the realisation that her memories were false,  because he was indifferent and jaded that the same was done to him.   But her pain made him reflect to the time he discovered his true nature,  and he softened. 

If you still have to ask the question whether he's a replicant or not,  perhaps Scott was right.   Not trying to be rude,  but he's probably tired of people missing the obvious.