Flying through known or forecast icing

wrote:

Not to tangent too much, but doesn't that regulation regarding "prohibited
flight into known icing conditions" without certified de-ice equipment loophole old
planes? I seem to recall something about if the POH for the aircraft does not say the
magic words, "Flight into icing conditions prohibited," then it's not illegal.

Right. The prohibition is not in the FARs, it's in the aircraft's airworthiness
certificate. The POH is derived from the airworthiness certificate.