Concerning those in a coma, they were sentient and the question is often whether they still are or will be again, but they definately were. Luckily we have not totally gone to the brave new world of classifying people as non-human
Until it can be displayed that a man-made device differs from a can opener or a desktop PC, its all appearances.
Should artificial limbs and mannequins have rights because they "appear" human. Better yet, how about my daughters Webkinz pet? It appears to be just as interactive as any robot, once you accept that life isn't a qualifier.
This is why I suggest that we should be thinking in terms of prohibitions rather than rights. (see post 1) Suppose we ban or sanction violent video games? Is this the same as giving human rights to computer-generated characters? Not really, but it has the same effect.
The point is not to protect soulless things, but to prevent feeding raw meat to those with violent appetites, even if it is imaginary.