Quoted from Crispin:I think Deckard being a replicant as well only adds to the story. Little hints along the way; when Brion tells him he's little people and he takes the job reluctantly. When Gaff tells him on the roof "you've done a mans job!" When Deckard picks up the unicorn that Gaff left him as Rachael walks to the elevator, he realizes fully who he is.
Hints yes, but it *takes away* from the emotional aspects of the story and there are too many inconsistencies. Deckard is WEAK compared to every other replicant he meets. Why have the weakest replicant ever made be a Blade Runner? He is more emotional than replicants. Deckard is the main human character in the entire movie. Almost all of the other main characters are Replicant's. It would take away the human element, and there would be virtually no human element to the entire story.
Here is a list of reasons that I saw listed elsewhere as to why Deckard is not a Replicant:
1. Deckard expresses feelings throughout the film, including his distaste for ‘retiring replicants’, and shows emotion facially which none of the Nexus 6 replicants do; even the super-advanced model Rachel has difficulty expressing feelings (the Voigt Kampf test is used to detect the absence of emotional response in replicants)
2. Deckard was married – this is not an implanted memory like that of a replicant, but is stated as a fact by Deckard
3. Deckard is afraid of being one of the ‘little people’ – none of the replicants exhibit fear
4. Apart from their programmed aggression, the only emotions replicants appear to have developed centre around a desire to extend their lifespans
5. Deckard demonstrates complex reasoning and sustained emotional responses, unlike the replicants whose conversation is stilted and whose thought process are limited by their programming to task orientated behaviour
6. Only Roy and Pris appear to demonstrate any affection for each other and this is relatively shallow
7. All the replicants are aware of what they are, except for Rachel who very soon realises she is not human – Deckard’s humanity is entirely natural and is fundamental to his personality
8. Deckard’s dislike for Taffy and his club appears entirely genuine
9. The police chief has used Deckard’s services for many years, whereas Roy’s gang are Nexus 6 – the current highest spec commercial model, so Deckard could not have been made better at an earlier time
10. Deckard does not require or carry any photographs
11. Deckard does not have the physical strength or endurance shown by the replicants, e.g. he is easily defeated by Leon and would have been killed if he not rescued by Rachel, physically he is powerless against Pris even though she has only days to live, Roy has the strength and speed to stop Deckard from falling and haul him to safety at a time when he is unable to save himself
12. There is no suggestion that the other blade runner shot when testing Leon is a replicant
13. The unicorn dream sequence introduced in later versions was inserted only as an attempt to substantiate the idea that Deckard is a replicant
14. The origami unicorn Deckard finds outside his apartment stands perfectly well in the original version of the film as a symbol of fertility and good fortune – hence Deckard’s self-affirming expression at finding it, rather than alarm he would have expressed at being given a message to confirm that he was a replicant
15. If Deckard had any inkling that he might be a replicant, he would have checked to see if he had any records at the Tyrell Corp at the same time as he checked Rachel’s records – clearly he did not
16. Harrison Ford appears to be pretty well convinced that the character he played in the film was not a replicant
17. The movie is more coherent with Harrison Ford’s narration, cutting it is an attempt to rob him of his humanity and therefore inhibits the impact of the film
18. Rachel exhibits more human qualities than the other replicants because she is an experimental model. If Deckard was a replicant, he would be an earlier model even than the Nexus 6 and would have none of Rachel’s sophistication.