>The dollar will start to seem unstable and useless. If you buy most things online, and if everything online is priced in Libras, then you’ll end up living your life denominated in Libras, and only converting your Libras into dollars on your occasional touristic visits to the physical world.[4]

This is so off the mark. Governments require taxes to be paid in their currency. So at minimum 30-50%, depending on the country, of all economic activity is guaranteed to take place in the local currency. Second, if the Libra fluctuates wildly with the local currency little will be priced in it. You don't want to sign a contract that could befome 20% more expensive because of a currency swing.