That makes sense, especially considering that the chains are meant to link other people together too, except all the quotes say 'in', and it doesn't sound like the context you'd use for something glued to the outside. For example,
Naminé: Yes, but first I have to undo the links I made. Then I have to gather up the memories scattered in your hearts and reconnect them.
If the chains were on the outside, then the analogy would follow that she pulled links off. Why then would they be scattered
inside the heart, in that case?
It's the same when she says "the loose links will sink into the darkness in your heart."
I think that explains what happens when you forget something; it sinks deeper into your heart, "lost in the shadows of your heart". I think therefore, the chains probably pass
through the middle of the heart, connected to other people on the other sides, rather than stored inside or glued to the outside.
I think you're right about them staying there when the heart fades, but I don't think it's cause they were just wrapped around the outside. I can picture it as if the heart was made of something like ice, and the chains metal. Even if the heart itself were to melt away, the chains would still remain. Perhaps the heart being eaten by darkness is like that; hearts don't have a form,
according to Nomura. So, when the darkness floods in and takes a heart, perhaps on the metaphysical plane all this must work on, it takes only the heart itself. And then, just as you said, the chains remain 'hovering' inside the Nobody.
Though, something about not having a heart to go with the memories must damage or limit them, I think. In the Days novels at least, Axel says he doesn't remember everything about Lea, and he also talks about how memories are fragile and easily warped things, and wonders what that means for Nobodies who base themselves on the memories they have.
I think Sora had a vessel, shaped by Kairi's memories (according to Nomura), probably a light-based body. I mean, if Heartless can have bodies based on darkness then why shouldn't one also have a body based on light? Idk. Makes sense to me
