Unfortunately I do not know the thread you are referring to.

But just by reading this, I am not sure the rationale should be to match the number in the hirarchy of the programme, but rather the benefits that the card brings to the bearer. Among other things, with PLAT one gets access with a guest to the business lounges when flying any OW and 100% bonus miles. Is this matched by BMI Silver? If so it'd be an adequate match, if not the OP is being shortchanged.

At the end of the day it is not in the interests of *A not to match entirely all the benefits else even if status match many will remain loyal to OW and will not even bother trying out a few flights on *A.