And those orbs, which could be the Sea Ghosts, glow and move around; hence, they emit energy. Plus, they lead you to Yngol's ghost and then disappear after you defeat him. (much like after you learn a word from a word wall: the wall stops emitting energy and stops chanting).

I'm not saying that it's a fit--just that it is very coincidental. 

So you tell me that if the walls can chant and transmit knowledge only to the Dragonborn they're not magical? Sorry, but in that case I think you're wrong

Well, it's just that, a theory. Not everyone will find it plausible, but I think there's more evidence than just Odahviing's "passing comment"(Dragons don't seem like the type for idle words, anyway).

I honestly don't disagree with you, Shor. Jurgen concluded that it just had to be the Way of the Voice after one major defeat. We don't know how many victories the Thu'um led them to. Then again, the Way allowed him to totally outclass the militant Tongues. Either way, though, it's not like Jurgen or Paarth kept the Voice to themselves.

Not a bad idea. I could easily imagine a word wall exerting some of the same power over the dead that a dragon priest might. Perhaps that's part of why they have lasted.

Eh, kinda. I think it's more due to generations of Nords not caring enough to pursue it. I suppose if ALL the Tongues in Jurgens time joined him, then yeah, that could be considered the case. But it even affects the modern Greybeards, who've only got four members left. Sure they never had a lot, but there were more than that. It seems more a matter of the Nords not trying to learn it, then the Greybeards hoarding the knowledge.

I can't see the connection between Paarthurnax forcing the WotV onto dragons means he's started a whole new Dragon Cult.

I agree, in part. For the majority of the modern Nord generation, yes, they did not pursue instruction in the thu'um. However, I am not certain that the reason was that they did not care. The Nords hold this sort of reverent awe, mystique if you will, about the Greybeards and High Hrothgar. (you can see this in the LDB's conversation with Balgruuf. Balgruuf practically has a nerdgasm talking about the Greybeards). This mystique engendered an "I'm not worthy to climb the 7,000 steps" mentality. I personally believe that the Greybeards, all the way back to Jurgen, fostered this mystique to perpetuate the Way of the Voice philosophy, which is nothing more than "use it only for worshiping the sky."

However, we do know that some have chosen to train with the Greybeards. Ulfric being one of them. Clearly, though, he rejected the Way of the Voice and followed a path similar to the Tongues. If Ulfric did it, others most likely have too.