Well, as long as Yama recognized the letters written on the crossed-out Vongola cressed, he could have written the sounds down in hiragana even without actually knowing what the word meant. It does look like he was starting to write in the final panel from the last chapter, too, after Kaoru had already taken off, so at least part of the message was definitely written by him, I think.
But since most of the message was conveniently covered up by the time Ryohei and later Reborn got there, someone definitely came back and messed with the evidence, so it is possible that whoever did it (and it might not necessarily have been Kaoru; Adelheid or someone else might have arrived at the scene) wrote the "sin" bit deliberately, it's true. If they did, it was one hell of a move on their part, since it had exactly the intended effect.
And whatever the case, it's pretty clear that Enma does intend to drink the sin, as you said. Maybe they're under the impression that it's the SOURCE OF THE MIGHTY VONGOLA FAMILY'S POWER or some weirdness like that. Who knows. But yeah, I generally agree with you there.
Re: Crackpot Theory
But since most of the message was conveniently covered up by the time Ryohei and later Reborn got there, someone definitely came back and messed with the evidence, so it is possible that whoever did it (and it might not necessarily have been Kaoru; Adelheid or someone else might have arrived at the scene) wrote the "sin" bit deliberately, it's true. If they did, it was one hell of a move on their part, since it had exactly the intended effect.
And whatever the case, it's pretty clear that Enma does intend to drink the sin, as you said. Maybe they're under the impression that it's the SOURCE OF THE MIGHTY VONGOLA FAMILY'S POWER or some weirdness like that. Who knows. But yeah, I generally agree with you there.
I'm loving this arc so much right now, oh man.