I hold the philosophical position that if two things are indistinguishable, their difference is irrelevant.
"What if we live in a simulation?" -- irrelevant
"What if you couldn't tell the difference between taking to a computer and a real person?" -- irrelevant
But more precisely, it's begging the question to say "imagine something was indistinguishable, now how would you treat it differently???"
@nomi It is the same with anything that can have no effect. "What I'd there are an infinite number of alternative universes that we cannot interact with?" Irrelevant.
On the other hand the question is always nor ever or just not yet? Is reality a simulation? Irrelevant until either the simulator decides to alter or end the simulation. Is it a computer or a human? Irrelevant so long as they truly are indistinguishable, but I would always have a suspicion that at some point I would discover a distinction.
I think the possibility that two things that are indistinguishable may not always remain so drives a lot of the debate on these topics.
@antares to your question of "ever or yet", I think the answer is that it only matters if you can differentiate it right now (whatever the relevant timeframe for taking action is).
At its core, it's a question of unknown unknowns. Suppose you are in 1450 and you're curious how the water in two cups is different. Could you even fathom microbes? Even if you could, it wouldn't be meaningful because it's fiction to you at that time.