I'm not sure about that... Doesn't 0-conf safety require that miners abide by the 1st-seen rule? What FreeTrade describes here can be called "accidental RBF":
The unintentional mining of a 2nd-seen double-spend tx with higher fees not because you support RBF, but because you have a hard lower limit on fees which the 1st-seen tx didn't cross.
What if a payee accepted the 1st-seen tx as valid, relying on the fact that most nodes have also seen it first, and assuming miners enforce the 1st-seen rule?
