It matters because talking to a human is a worthwhile thing to do, but talking with a probalistic robot commentor is not, beyond some level of diminishing novelty.
Instead of median, what if the produced output is indistinguishable from the 99th percentile commentor (meaning, "genius" level commentor)? Would it still be valueless? In what sense?
But at a higher level, talking with a bug or robot or rubber duck, no matter how smart it sounds, isn't very valuable. There is no mind to change on the other side of the conversation. There is no life that is being lived on the other side of the screen, the experience is entirely one sided.
The max possible value, imo, is at the level of playing a video game vs a bot. It could be fun, you'll probably improve at the game, and maybe you'll learn something, but more than that? I am deeply skeptical.
False, it would be even more valuable to the typical HN user. (You and I are not typical users.) The typical user lurks and reads comments only. If there were more discussions on more topics for the typical user to read and learn and make up their mind about things; then that would be valuable, even if those discussions were algorithmically generated.