> They are both equally money.
I think its actually "MB" you're talking about, not M1. M0 for coins + physical bills. "MB" would include Federal Reserve deposits. For whatever reason, its different than M1...
They are considered "equally money" because its "Equally trusted". Banks can turn Federal Reserve deposits into Cash, and vice versa. Your savings account, checking account, and so forth is similarly "equally money" because you trust the bank to give you the cash when you need it.
And once again: the Fed can't create M0. So that right there is a major disconnect between M0 and MB / Federal Reserve Deposits.
But Federal Reserve Deposits are not money. Like a savings account, it generates an interest rate. In effect, Federal Reserve Deposits are "like money" because everyone trusts them very much.
If the Federal Reserve plays too many games with its Federal Reserve Deposits, there may become a mismatch in the trust of MB and M0. A dangerous game for sure, so its a good thing that QE has stopped.
> The reason the Fed doesn't buy unlimited amounts of whatever it likes and grow its balance sheet forever is that this isn't consistent with its mission to fight inflation.
Bingo.
Because the Fed as an entity believes inflation should be at a certain level. Not too high, and not too low (aka: negative or deflation).
> The Fed never has to pay anything back because people are very happy when you pay them for stuff using U.S. dollars.
On the contrary. Inflation is precisely when people aren't happy for being paid in US dollars. Things cost 10% more because people trust the dollar 10% less.
If the Fed never pays anything back, inflation will grow (aka: people trust the dollar less and less). The reason why inflationary monetary policy was fine in 2011 through 2014 was because DEFLATION was the main worry.