You're right, this is not possible. What caf may have been thinking of is that banks may borrow money subject to other conditions, such as by emitting bonds, to

You're right, this is not possible. What caf may have been thinking of is that banks may borrow money subject to other conditions, such as by emitting bonds, to which the 100% reserve requirement doesn't apply. Of course, such a system is also subject to bank runs, just via a different mechanism ("run on bonds" by lenders refusing to roll the bonds over instead of run on deposits).