Oh, I see what you mean. This looks like a bug, @lubos. The account, Special Accounts, has appeared spontaneously in the chart of accounts, with no ability to designate it as a control account, so it could not even be renamed for normal usage as a control account. And it cannot be deleted:
I am splitting this portion of the thread off as a standalone topic and putting it into the bugs category.
This bug may be related to this one: Bug - Control Accounts.