I started to wonder about that after seeing the following tweet.
Fontase is well known for pumping and dumping litecoin.
Since nubit is stable, it is obviously not possible to pump and dump nubit in the original sense of the term.
However it is possible to try to manipulate its price.
For example, Fontase could try to sell a lot of nubits at 0.5 usd or buy a lot of nubits at 1.5 usd.
But obviously he or she would have to undergo a huge loss, assuming that he or she would find each time a buyer and a seller who cannot be liquidity providers.
So not only, Fontase would be punished financially for doing so (however, we can imagine some scenarios in which the goal is to destroy the peg so incurring a loss is not strictly prohibitive), but also he or she would probably find only a tiny liquidity assuming the peg is produced mostly by liquidity providers that are rewarded for tightly keeping the peg, thus preventing them from matching the quote of Fontase. So in the end, even if Fontase is ready to incur a loss, the extent of the manipulation would be isolated and the damage to the peg negligible.
Any other ways that you can think of?