As of this posting, Blizzard has re-enabled the creation of illy accounts on all 4 realms of Classic Battle.net, with exception to the @ symbol.

The @ symbol has been disabled due to issues with channel banning specifically:

We mistakenly reactivated the ability to create account names with "@". Such names cannot be banned from channels and present other problems for the community.

See Blizzard's original announcement for more info.

Looks like the solution that Blizzard has moved forward with is as follows:

Accounts with @ symbols have been deleted and cannot be created.

symbols cannot be created. Accounts with "illegal" symbols, with exception to @ , remain intact.

, remain intact. Accounts with "illegal" symbols, with exception to @ , can still be created. For instance, I just created the accounts (((Carl)))@USEast and {Carl}@USEast .

Update Feb 10, 2017: Blizzard has not actually deleted accounts with @ symbols in their name and will be preserving accounts created with them. More info in Clásico's post.

Best,

Carl Bennett | carlbennett.me | bnetdocs.org