At this point, I see as the real concern is that China, or anyone - including the US or other private sector, isn’t buying our bonds then we (the FED) has to buy them from ourselves?
Redeeming some holder’s short bonds and then buying our own long bonds...this just another form of kicking the can to delay the inevitable.
If it wasn’t government doing it, I think it would be illegal - or should be. Sort of like the analogy of borrowing on one credit card to pay what is due on other CCs. And we know how that always works out.
China does hold 7% of the U.S. national debt--
-- but for some reason everyone wants to loan the U.S. money (from here) including (believe it or not): Russia $81.7B, Mexico $85.9B, Colombia $37B. and Kazakhstan $24.4B! As far as buying back debt, the way it works is a person (or a government) can borrow from others what ever others are willing to loan, but there's never a limit on how much folks can borrow from themselves. imho it's not really "debt", it's just pretending to have lots of money saved when you actually already spent it.