In the past, when we played with tokens on-chain, there were basically two specifications:

1️⃣ Fungible: Just like money, a 100 bill is no different from another 100 bill; they are interchangeable and can be divided. For example, ERC-20 tokens.
2️⃣ Non-Fungible: Each one is unique and cannot be exchanged. Like NFT artworks, concert tickets with seat numbers. For example, ERC-721 Token.
And the Fungible Duality created by @burnt_xion directly combines these two characteristics.
It means:
The $XION in your hand can be spent, split, and exchanged like money.
You can also add unique features to it (such as a specific number or special attributes);
It can even split while maintaining uniqueness at the same time.
In this way, a Token can serve as both currency and carry special value like an NFT - it's somewhat similar to that "limited edition 100 yuan" in your wallet, which is both money and a unique collectible.
I think if this is used well, it will make the gameplay and business models of Tokens more flexible, especially suitable for scenarios like games, membership cards, tickets, and on-chain identities.