In re-reading my post on Prof. Fish's attempt to correct the syntax of an AT&T call center employee, I'm led to wonder whether his cri de coeur ("It is a factual matter as to what is and is not syntactically correct") is itself syntactically correct.
The basic construction here is what is traditionally called "extraposition from subject" (see e.g. here for further discussion and examples). It involves an expletive pronoun it (sometimes also called a "pleonastic" or "dummy" pronoun) in subject position, standing in for a sentence-final clause that might have been the subject:
It's a shame that things turned out so badly. = That things turned out so badly is a shame.
It's not clear what she wanted. = What she wanted is not clear.
It's odd how well the timing worked out. = How well the timing worked out is odd.
So the sentence "It is a factual matter what is and is not syntactically correct" would be normal, though awkward because of the three repetitions of "is", the hard-to-parse "and", etc. The version with the what-clause in subject position would be "What is and is not syntactically correct is a factual matter". However, adding "as to" between "matter" and "what" is not only redundant, but (it seems to me) probably ungrammatical.
Certainly the result of putting the whole final constituent in subject position seems quite bad to me:
*As to what is and is not syntactically correct is a factual matter.
And even more obviously, the what-clause doesn't work as the subject:
*What is and is not syntactically correct is a factual matter as to.
So alternatively, we could try to analyze the initial "it" not as a dummy pronoun, but rather as as a regular pronoun, referring to the question of what is or is not syntactically correct. This would work if we set things up with an initial prepositional phrase:
As to what is and is not syntactically correct, it is a factual matter.
That sentence is pompous and awkward, but grammatical. However, this kind of pronominal reference generally doesn't work when a pronoun in a main clause tries to refer to something introduced later in the sentence. For example, compare
As to her motivationsi, theyi are hard for me to understand.
*Theyi are hard for me to understand(,) as to her motivationsi.
And similarly, I think that it doesn't work to analyze the initital "it" of Prof. Fish's sentence as referring to the distribution of syntactic correctness, introduced in the later clause headed by "what":
*Iti is a factual matter as to [ what is or is not syntactically correct ]i
My conclusion is that in his distress, Prof. Fish got confused, and began his sentence with one construction while ending it with another. That happens to all of us from time to time.
Perhaps I've missed an analysis — if so, please point it out in the comments, since this is one of many occasions in life when the lesson of John 8:3-11 is worth pondering.
[Let me note that just as there are plenty of examples out there of redundant pronouns like the one that enraged Prof. Fish, there are also plenty of examples out there of the construction that he used in complaining about it. Here are a few of them:
It's strange as to what's happening.
It is a factual matter as to whether the certifier has read the MDR regulation, whether the company has established a system to implement those regulations, and how many MDR's the company submitted to FDA as a result of following that system.
Given the weight and density of concrete and the massive pumps that are required to do this, it's obvious as to why it's a difficult task.
Wobuffet is an uber and it's simple as to why.
In the case of the redundant pronouns, it turned out that the phenomenon goes back to Middle English, though perhaps the analysis and the function have shifted. I wonder about the dynamics of "It is X as to WH-clause". Is this an old construction, or a new development? I also wonder about the sociolinguistics -- the examples that I've seen seem to come from two types of context: ponderously pompous contexts ("It is a factual matter as to whether the certifier...") and breezily sub-standard contexts ("... and it's simple as to why"). Does this impression hold up under examination? ]