The phoenixd server handles small first receives differently than mobile app Phoenix. The fee credit system might be interesting as a comparison, with the main caveat that small receives are only accumulated until they can be used to open a channel.
Discussion
I don’t find the “fee credit” system interesting for a consumer product at all (and I guess ACINQ broadly agrees given they don’t use it in Phoenix). The first payment is *the* experience that a wallet has to get right (and then every other payment but the first one matters a lot). If the first payment is just “thanks for the money, we’re keeping this to pay for fees in the future” I don’t buy that people would keep using that wallet.