Hi,
iChat 6 and Messages do allow AIM to verify the Password slightly differently to iChat 5 and earlier
iChat 6 an Messages also login to me.com
This dual login (to AIM as well) then allows the AIM servers to "See" the password.
No Login to me.com = no access to the Password.
However it only seems to effect newer iCloud Issued @me.com names
This means iCloud issued @me.com names will not work in iChat 5 due to this (Nor the AIM Settings Login point)
iChat 6 and Messages also use different Servers to iChat 5 and earlier.
The new one is api.oscar.aol.com On port 443. The old one was login.oscar.aol.com which gained a leading s when you used SSL. This used port 5190.
So there are ways that AIM could monitor how iChat and Messages login.
However it seems to be the older @mac.com names that are being effected.
If Apple were blocking the names then you would not be able to Login with that name to iTunes, Apple Support Communities and the like (however iMessages and FaceTime registrations are separate again from that)
For a long time AIM have suspended Accounts they see as having Unusual Activity and have had contact pages to get in touch with them.
Their first response has always been "reset the Password" (i.e if you own the Account then you can do this)
However with Apple IDs the process does not work as AIM don't have the Passwords they can only Look at them.
In the past I have come across to conflicting Apple Articles about how it works.
My theory is that Apple do Allow the List of Apple IDs to be either held or seen at AIM.
The Passwords definitely require AIM to Look them up at Apple.
One of the Apple Docs said that Apple "Created the AIM names at AIM" for Apple Users.
If this were true then people would not have problems with the AIM limit of 16 characters to a password.
I had forgotten about the reciprocal arrangement that AOL IDs could be used in iTunes
But in searching for the Docs I was talking about I see lots about losing that ability.
I have come across this http://support.apple.com/kb/TS4139
(I still can't find the Docs I was looking for)
It now looks like some tit for tat political stuff is going on.
However the issue is at the AIM end.
9:16 PM Monday; September 24, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and and iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously