It's actually a very interesting parallel between Balance of Payments and QE (dis)similarities brought by the author. However, what I generally lack in all discussions related to QEs (and QEternity in particular) is the distinction between the channels chosen for new money influx into the economic system.
The financing of the current account deficit is most likely done through purchases of Treasuries via primary market (i.e. newly issued Gov't bonds) rather than secondary (i.e. private) market. It's a genuine leverage in a sense, that existing money (i.e. export-earned revenues) is used to purchase newly created assets (i.e. "fresh" government bonds). In turn US government can use its coffers filled with foreign inflows to create fiscal stimulus, which triggers economic activity (the Keynesian view).
What the FED is doing now, is actually purchasing all kinds of assets in the secondary market from private sector. That is hardly any leverage, since all the freshly printed money will be used to acquire existing bank-owned assets. You might even argue that such actions constitute a (very backward but still) deleveraging of the system, since the FED is less likely to care if these MBS’es will default or not (by definition, the FED has no aim to earn profits on its assets), and thus in theory you could walk away from your property and be left with no debt afterwards.
And here comes the most confusing piece of puzzle that fails to explain how all that extra cash on banks’ hands will help boost the economy (or for that matter – even inflation), since (arguably) most of the new liquidity is channeled straight right back to the FED via reserve deposits. Essentially, this is the very same sterilized version of ECB’s Open Market Transactions, that leave the entire system cash-neutral on a net basis, yet allow the banks to get rid of the toxic assets.
Assuming that the US banking system had sufficient time to “detoxicate” itself after the financial crisis, and risk-taking in general is now in check due to stricter regulations of the banking system (think Volcker rule, Basel III), the real danger is that the latest round of QE will achieve exactly… nothing (?)