Discovered this in 1.13alpah, rev 35524. Setting $wgEmailConfirmToEdit = true; generates the following error message whenever an anonymous users tries to create a new account:
You do not have permission to create new user accounts, for the following reasons: You must confirm your e-mail address before editing pages. Please set and validate your e-mail through your user preferences.
I tried setting $wgGroupPermissions['*']['createaccount'] = true; but this did not resolve the problem.
I disabled all extensions and the error persists. This was not an issue in version 1.11.2 (don't know about version 1.12 -- never utilized that one).