Has Kakashi possibly read the Rikudou's tablet?
In another thread, I was discussing that Jiraiya would likely have a counter/know how to combat the Mangekyo Sharingan's genjutsu capabilities due to the fact that Kakashi had encountered it, developed a counter for it, and likely taught it to Jiraiya as Jiraiya was the one who would be protecting Naruto from Itachi.
Owarij, as intelligent as he always is, debunked this by pointing out Jiraiya never taught Naruto on how to combat it, he only taught him how to dispel basic genjutsu. It would seem extremely unlikely that he wouldn't have taught Naruto if Kakashi shared the information with him.
We can confirm Naruto doesn't know of the way to combat it by him being surprised once Kakashi points out not to look in to Itachi's eyes, as well as asking Chiyo for advice on how to fight a sharingan user.
So, what does this have to do with Kakashi having read Rikudou's tablet? Well, I had assumed that Jiraiya is where Kakashi got his knowledge of amaterasu, as he states he's never seen it before. It would seem to have been the most logical answer.
But with the doubt that Owarij pointed out that Jiraiya and Kakashi discussed their encounters with Itachi, it begs the question..how does Kakashi know of amaterasu? Even if Jiraiya and Kakashi did discuss the encounters, and for whatever weird reason he didn't teach Naruto how to combat the sharingan, how did they(or Jiraiya or Kakashi by themselves) figure out it was called amaterasu?
The first time we see amaterasu is here, and we learn of it's name is after Itachi and Kisame run away from Jiraiya here.
This could also be how Kakashi learned of how the mangekyo sharingan is activated(given against Itachi in part 1, he first learned about the Mangekyo Sharingan actually existing), and given that he experienced something so tragic in his killing of Rin, he figured he may have unlocked it already(which he had, but apparently just wasn't aware of it, or the other possibility being he just didn't have the control of the sharingan/the chakra reserves to pull it off, but given his encounter with Itachi, the safe bet is he didn't actually know it existed).
Is this a goof by Kishi or will he reveal that Kakashi has read the tablet?