Again, there's no single clear understanding of the claim (by post-Keynesians et al.) that banks create money out of nothing.
For example Varoufakis in a talk referred to Certificates of Deposit (CDs). So in this specific case CDs are said to be money created by banks. But if we look at a basic definition of a CD we read:
To buy a CD, customers agree to deposit their money for a specified period of time. The shortest timeframe is usually one month, with the longest running up to five years.In return for committing their money for a period of time, the customer earns interest. The interest rates are pre-determined by the institution, and typically remain fixed over the length of the CD - though some institutions may offer CDs whose rates can increase. The longer the length of the CD, typically the higher the interest rate paid.
When the CD's time period is complete, a CD is said to “mature.” Shortly before this, the institution will notify the customer, offering them the option to either withdraw the money with interest earned, or re-invest the money for another period.
http://www.investopedia.com/video/play/certificate-deposit-cd/
So when a bank issues a CD, it does not at all create money out of nothing, but on the contrary borrows money from customers in order to use it, which otherwise would be sitting idle (in the customer's pocket). The same as with ordinary bank accounts.
CDs pay slightly higher rates than savings and checking accounts because the customer commits to not withdrawing their money for a specified period of time - whereas money in savings and checking accounts is able to be withdrawn at any time.
I already mentioned Keen (linked an interview where he apparently tried to reject 100% reserve by arguing that if the bank would lend out the money of someone else's deposit to you, and then that someone else wants to withdraw money, how can the bank give that money to them, since it is still lend out to you...)
That notion is correct.
(btw on gold, since 2011 JP Morgan accepts it as collateral "to satisfy securities lending and repurchase obligations with counterparties")