This is exactly what keeps it at $1. If someone is willing to sell at $.99 then the number of buyers is gigantic. Ditto with someone buying at $1.01. That’s why it’s news when the peg drops by more than a fraction at a penny.

As for why would someone buy or sell for other than $1.00? Plenty of reasons, if a market opportunity to make 10% in a crypto investment pops up, damn right people will liquidate tether at a slight loss

Tether is not willing to do this

So their idea of pegging is just a forcefully worded request?

"Sure, it's pegged, Anyone who fills in the right forms can get their USD back. After a few weeks. And if the request is big enough. Oh, but there was a problem with your form. Sorry. Try correcting it and resubmitting it. No, we can't tell you what the problem was."

More of a vague promise to buy. They have a lot of dollars. If tether skips to 99 cents will they buy it from people to push the price up? Maybe.

It’s been sitting at 99.9 for several days now.

Tether will only redeem amounts of $100k or more. The vast majority of people get out of USDT by selling it on the market.

Depending on how many people want to sell, how quickly they want to, and how many market makers are willing/able to arb it back up to $1.00, you might just take $0.99 instead.

Those who bought it at 0.9999954 and resell it at 0.9999978, making less than pennies on the dollar, but still profit. Then you make a chain of suckers until it goes back to 1USD