I absolutely think Kino went insane and imagines Hermes talking. Maybe everything else that happens actually happens (her country can’t be the only weird one), but she still hears a voice that isn’t there.
I’m really curious if most people figured out the twist or not. I saw the 2003 anime a while back, so even though I didn’t remember any of the details of the chapter, I did remember that there was a previous Kino and the Kino we know met him previously. Though even if I didn’t already know, the way Kino spoke in this chapter was pretty different, so it felt obvious to me (though it’s possible I was only noticing since I already knew).
This was easily the best chapter so far. The last line alone could be enough for me to buy the next book or two, assuming I can confirm that the story that takes place after this chapter is in one of them.
By the way, is there a typo in the last sentence of the chapter? For 尽くせない, the 尽 has the furigana つく instead of just つ.