We have the same sort of thing in Australia where the Regulatory folk hold varying delegations under the Regulations. However,
If your friend provides you a letter, on FAA letterhead, giving you an "interpretation" of the regulation and you're subsequently violated for following this interpretation, you can't use it in your defense, because that letter has no authority.
rather surprises me as it would infer that the member of the public needs to "know" precisely what delegation the Regulatory representative holds. I would have expected that the opinion might well be set aside by a Court but that the member of the public relying on an apparently valid opinion would not, as a direct consequence, suffer a penalty.
So far as the spirited discussion above is concerned, I am taking the view that both SNS3Guppy and 411A are senior Industry folk with broad shoulders and well able to withstand a little professional criticism from each other. I am sure that neither will overstep the bounds of reasonable, if spirited, constructive criticism.
Meanwhile the rest of us can read and take in the detail from the discussion.