Having read through this excellent thread I noticed there's however a contradiction to this lore that I'd really like to clarify (I'm really sorry to Ferne, as he's done an awesome job trying to sort out all the lore for us) - and that's the constant reference to the Echo being 'time travel' - it's not, at least, not in the literal sense.

In reality, to me it's more of a form of clairvoyance/telepathy, reading a person's memories and actually 'placing yourself' in them in a kind of dream state - Minfilia mentions this and explains how the Echo works when you first arrive at the Path of the Twelve:

Quote Originally Posted by Minfilia
"The Echo allows you to breach the wall of a person's soul, and hear the resonations of their past. You will be there in their memories, seeing things as they saw them. You may even interact with that lies therein. However, the past is like a stone tablet. You cannot uncarve what is already written."
So really, what we all experienced in the first part of the game is not the literal past, but a kind of dreamworld taken from ten year-old memories (when I read that line of Minfilia's memories of FFVIII came back to me - in fact, the very nature of the Echo itself was a lot like Ellone's power in FFVIII.).

The big question is, exactly whose memories did we access during the first part of the game? Especially the very start - if for instance in the Gridanian storyline Papalymo and Yda aren't actually there when you first arrive in the Black Shroud, then who was it then that the Echo accessed memories from? I really hope Ferne can shed some light on this as it's really been bugging me for a while now.