Mortgages can change repayments amounts as the central lending rate changes.

Not in the US if you have a fixed rate mortgage, and most do. There's tons of people who locked in rates at below 3% back in 2020-2021.

yo dawg

The fed and it's balance sheet is independent from the treasury and it creates and destroys money at will. Where do you think all that Quantitative Easing money came from? It wasn't an act of congress to allocate the cash, it wasn't the treasury issuing bonds. What happens to the money the fed receives when the QE bonds it's holding mature? If the fed doesn't reinvest it, that money is effectively removed from the money supply. The fed doesn't issue anything when it creates currency. It's all accounting.

None of that really matters because the fed doesn't mark to market, and losses the fed takes doesn't matter. If anything the current situation means the fed isn't giving it's "profit" to the treasury anymore. It can eat losses because the cash account on the fed balance sheet might as well be an infinity symbol.

It drives me nuts that little girl pants have no pockets, but boy pants do!