The duplicated people is imaginary and hypothetical, happening (or not) in an unspecified time in future; the suffering in animal farming is real and happens today.
Somehow many people are ready to ascribe personhood and have ethical considerations towards computer programs and other digital entities, while not being much concerned about the suffering of animals that actually exist today in the physical world
Yes, there's a difference between suffering that happens now, and potential suffering that happens in the future, caused by research being done now. I see many in this discussion (me included) have not made this distinction explicit in all their comments but I also think it should so be obvious that any counter-comment which appears to not understand that this distinction is being made implicitly is best explained as missing the point deliberately.
Anyway to reiterate my point upthread, there could be people who think a chicken-level entity suffering is permissible, and a human-level entity suffering is not, and it is a perfectly consistent moral position for them to say we should not do research into creating new kinds of human-level entities with the potential for suffering. The permissible suffering being in the present and the impermissible suffering being in the future does not really change that.
PS in this thread we were not only talking about computer programs, but artificial brains made from biological human neurons too.
Somehow many people are ready to ascribe personhood and have ethical considerations towards computer programs and other digital entities, while not being much concerned about the suffering of animals that actually exist today in the physical world