I don't know the mechanism of UST/LUNA (I don't have any investment in LUNA. So lucky I am)
I just think if LUNA/UST can swipe 15b market cap so 150m of HIVE can also be swiped.

What usually happens when the debt increases and HBD is close to the haircut limit, or above it, more HBD is starting to be converted to HIVE, as users exit it, and the HBD supply drops.
As the HBD supply drops so does the debt level. In this way, the debt limit provides a balancing for the system as it forces users to exit HBD and reduce its supply. At the end it all depends on the price of HIVE

What if the users exit HIVE because of the low HIVE price and debt level increases again, then HBD loses its pegged again, users keep exiting HBD and then exiting HIVE ... Does it look like a death spiral?