A usenet service charges a network fee for monero payments via BTCPay of 1.9e-9 XMR. This is described in this FAQ as:
Network fee (cost) is a feature in BTCPay which protects merchants from customers who pay the invoice partially. When an invoice is paid from many outputs, the fee for a merchant who needs to move those funds later will be higher.
For example, the customer created an invoice for 20$ and paid it partially, paying 1$ 20 times until the invoice is paid fully. Merchant now has a larger transaction which increases the mining cost in case the merchant decides to move those funds later. By default, BTCPay applies an additional network cost to the total invoice amount to cover that expense for the merchant.
The network fee is 5 orders of magnitude less than the default mining fee, and 4 below what would even register on their exchange rate calculation. It is not obvious to me why the company chooses to charge this apparently meaningless fee. Is there a non-economic reason to do so?
