I watched this earlier... and... I don't see the link between Deckard being a Replicant. Mainly because he doesn't have the super strength... when he was hanging on the ledge.. In theory... if he were a Replicant.. he would have been able to pull himself up. Either way... that's my take on it.
the links in the movie are:
- the most obvious one is the unicorn dream, and Gaff's unicorn origami: this is to show that Gaff knows Deckard is a replicant, as Gaff knows Deckard's private inner thoughts and dreams, so they must be artificial.
- Deckard is obsessed with photos, just like the replicants. Check out his piano, there's tons of photographs of family. Photos provide tangible "proof" to the replicants artificial memories.
- in one scene in the apartment, Deckard's eyes glow like the other replicants.
- in the original theatrical release, they misnumbered the ## of loose replicants due to a script continuity error, which many thought was left in at first as a clue that Deckard was the last loose replicant.
- some other speculation: what better way to catch an android, than to use another android?; Ridley Scott has stated that he intended to make deckard a replicant from the beginning, he also speculates whether Deckard is a Nexus 5, a Nexus 6, or a Nexus 7- meaning that his level of strength would be more or less than the Nexus 6 replicants in the films; the abiguity is implied in the original novel as well.
i personally feel like the correct answer is whatever you choose, it reads both ways equally well...