Rusty Russell expressed concern that limiting the unit to satoshis could render the system inoperable as fees are frequently sub-satoshi. However, Glasbergen argues that staying within the limits of the base layer while achieving benefits from second-layer scaling is important for optimal security. While keeping satoshi as the smallest fraction ensures everything done off-chain is valid and enforced by the chain when needed, it also means users will overpay if someone routes their payment and charges a small fee. The dust rules prevent creating an output smaller than the dust limit (546 satoshis on Bitcoin), meaning transferred values and fees must always be multiples of that dust limit. Glasbergen suggests analyzing the consequences of allowing this choice and coming up with a proposal to add support for it, but acknowledges that too many options can increase complexity. Ultimately, finding the right configuration options is important, as few users will care about their unit of transfer, especially if it's handled automatically for them.