Also the situation this commenter has presented: the author explicitly says the story is not about slavery, but the reader insists it is on the account that the writer's subconscious laced slavery within without her knowing. That's not really drawing parallels between the story and slavery anymore; that's saying the author herself wrote slavery in, and just didn't know it.

I don't think this is what nakedsamurai means by "a science fiction short story that, to me, very obviously has connotations about slavery." You are (ironically) reading a lot into the comment that isn't supported by textual analysis.

Blade Runner is actually an interesting example in that Ridley Scott thought Deckard is a replicant but Harrison Ford, who actually portrays the character, thought he was human, and Scott's direction deliberately leaves ambiguity: the evidence your friend found was left by Scott deliberately. Actually for me the entire impact of the film rests on never knowing which, and I much prefer to watch the film every time looking for evidence either way, as if there was no authorial comment. The whole experience of Blade Runner then becomes an inquiry into what humanity is and how it might be different from a near-perfect imitation. That's much more satisfying to me than simply watching a film about a robot. It's also worth noting that the story and the world in which it was set were created by Philip K Dick, and in his book Deckard is explicitly human.