phiefer3, SE is not known for its great writing, though they've known a few shining moments now and again. That's pretty well known. Their storytelling, especially in sequels and prequels, is usually laden with cyclical rationalizations and plain ol' revisionist nonsense.
I gave you my rationalization for that one, and a thread snipped at both ends is logical enough for me. Overlook the oddities, because there's no way to completely justify them. Many have tried over the years. Or stop buying SE games; vote with your cash for better writing.
BTW, SE probably will include a third-arm growth ability at some point, to stop players from discussing it further. ;j
Guides and other contributions: http://www.esque.com/slr/gamefaqs/ FFX, FFXII, KH, KH Re:CoM, KH2, Okage: Shadow King, Secret Agent Clank
I thought everybody forgot who Sora was because of his Nobody?
They reversed the Nobody process & then everyone remembered him again.
They could probably do that with the other Nobodies if they tried, send them to a digital world & alter their memories so that they succumb to joining their Self again.
(Though it'll end up I'm missing a point somewhere)
Edit: Infact this is the only case when you know the Self & the Nobody, whereas all we know of other characters are just their Nobodies. Their friends could've forgotten them too, but we wouldn't know.