Oh, and "professionally-qualified grammarian" isn't hyphenated. Great example of irony though.
I think we live on different planets. We certainly read different grammar reference books. Looking back through the posts, I have noticed that you go aggressive early. You might want to curb that.
"Professionally-qualified grammarian"? You might want to check that.
By your logic, "very qualified grammarian" would be hyphenated.
When a compound modifier includes an adverb, a hyphen is only used to eliminate ambiguity (i.e., when the adverb could feasibly be an adjective). Examples are best known player, well fatted calf, and fast evolving process.
(I'd take the hyphen out of "professionally-qualified grammarian" if I were you.)
You said: If the word "professionally" is dropped, it becomes ungrammatical since you can't say a *"professionally grammarian".
I don't understand that. If the word "professionally" is dropped, it becomes "qualified grammarian", doesn't it?
You initially asked a question about antecedents (the answer to which you failed to grasp) and now you are arguing about compound words vs syntactic constructions.
You're clearly here simply to cause an argument, and not in the least bit interested in learning about grammar. Why you asked a question here is beyond me.
Further, who were you hoping would answer your question? Some non-native speaker - perhaps a learner from China?
Wouldn't you prefer a grammarian who understands these things and can give you a decent answer? It seems not.