I'll throw in my 2 cents. It is stated that the current tablet, which is a 100% fabrication by BZ, needs the Sharingan/MS/Rinnegan to decipher. I think we can all agree to that. But.... whose to say that the ORIGINAL tablet did, or that it needed a Dojutsu at all to read? If Hagoromos true purpose for the tablet was to warn his children, and transmigrations to reconsider their attempt to aquire his power, why would he encoded it in a way that could only be deciphered AFTER they had already done what he had written for them NOT to do? I believe the original tablet had no such writing, he wrote it for both his sons, one of which did not have a dojutsu. This is how BZ was able to read the tablet, and its not that difficult to write a message in a manner that you yourself cant read. Its doable that BZ merely wrote the new message in a manner that needs a dojutsu to decipher.