Fee rates in Bitcoin Core are measured in satoshis/kB.   There are a couple
places where a minimum of 1000 satoshis/kB is assumed.

Setting "incrementalrelayfee" to a smaller than default value and either
leaving "minrelaytxfee" unset or also setting it smaller will be sufficient
to allow your node to accept and relay transactions with smaller fee
rates.  Of course without the rest of the network making these changes
and/or the miners being willing to mine those transactions, it won't be of
much benefit.

Fee estimation doesn't distinguish fee rates less than 1000 sats/kB.  This
would be more substantial to change.



On Thu, May 10, 2018 at 4:10 AM, st-bind--- via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Currently, the minimum fee of 1 satoshi per byte corresponds to about 0.09
> USD per kB, which is no longer insignificant. Maybe the time has come now
> to introduce more decimal places and make the minimum fee 1 of the new
> smallest unit. This way, everyday payments would again be possible with
> virtually no fee without flooding the mempool with free spam transactions.
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