Slate has a piece by Kitty Burns Florey, the author of Sister Bernadette's Barking Dog, in which she attempts to diagram a few of the more egregiously strange comments that Sarah Palin has made during her interviews.

As she notes, diagramming a sentence tells you nothing about the sentence's meaning:

One thing we can't learn, of course, is whether her words are true or make sense. Part of the appeal of diagramming is the fact that just about any sentence can be diagrammed, even when it is gibberish. Cats chase mice and Mice chase cats present the same kind of entity to the diagrammer. So does Muffins bludgeon bookcases. If it's a string of words containing a certain number of parts of speech arranged in reasonably coherent order, it can be hacked and beaten into a diagram.

Put another way, diagramming is supposed to reveal the syntactic structure of the sentence, or in the case of an ill-formed sentence, where the syntax breaks down. It can't speak directly to the semantics.

However, Florey's choice of sentences reveals another limitation of traditional diagramming, at least as it is generally practiced: it becomes a game of putting each word into its slot rather than a way to flag certain purely syntactic problems.

Consider the first of Palin's sentences that Florey attempts:

It's very important when you consider even national security issues with Russia as Putin rears his head and comes into the air space of the United States of America, where—where do they go?

Here's Florey's attempt at a diagram:

She comments:

I didn't have a clue about what to do with the question that ends it. Otherwise, in its mice chase cats way, the sentence is perfectly diagrammable.

But it is precisely the fact that she is unable to figure out what to do with the where clause that indicates either a syntactic problem or a misanalysis, so it seems like a bit of an overstatement to call the sentence "perfectly diagrammable." Read the way Florey does, Palin's remark looks like a cleft sentence, but never gets to the required "that" clause, veering off instead into a string of subordinate clauses from which Palin never extracts herself.

The trouble with the where-clause vanishes, however, if we take this as two sentences. That is:

It's very important when you consider even national security issues with Russia. As Putin rears his head and comes into the air space of the United States of America, where—where do they go?

If we read the as clause as subordinate to the question, we actually have two syntactically well-formed sentences (ignoring the reference problems with the pronoun). This is probably a more sensible reading and since the missing period reflects a decision by the transcriber of the interview. I'll leave the phonetic analysis to a someone more qualified, but my impressionistic sense when listening to the interview is that although there's not much of a pause between Russia and as, there is a falling tone on Russia, which is consistent with sentence-final prosody.

You can listen for yourself:

My point, however, is not to defend Palin. Her statement remains breathtakingly idiotic, whether it is syntactically well formed or not. Rather, I am struck by Florey's reaction to the apparent instance of bad syntax. By choosing to interpret the as clause as a modifier of consider, she goes down a garden path and has no way to slot the question into the sentence. However she remains satisfied because she has managed to put all the smaller constituents into place.

The fact that our parsing has crashed, however, suggests that we ought to do one of two things: either reconsider our analysis or show the grammatical problem in our diagram.

For all their limitations, Reed-Kellogg diagrams certainly could be used to do the first, if you approach them with the mindset: that is as a provisional exploration of possible interpretations rather than as a schoolbook exercise that has one predetermined solution. There's no standard way to do the second, however. Since they are intended for schoolroom use, there's little attention to working with ungrammatical sentences. Thus Florey is forced to leave the wh-question orphaned to the side rather than putting it into the whole sentence in a way that could direct our attention to precisely in what way the sentence is supposedly ill-formed.