A comma puzzle: The false-interjection error

If you enjoy puzzles about the comma—and who doesn’t?—here’s an elegant but very difficult one, courtesy of Daily Writing Tips where Mark Nichol proved it’s difficult indeed by getting it wrong, as did my wife, a short-story author with a postgraduate degree in English. But it’s not impossibly hard, since the first commenter on Mark’s blog got it exactly right. (I’ll delay the link so you can try it.)

In the form I’ll use, the puzzle requires you to choose the two correct versions:

Version 1. Residents decide driving, and shorter trips to places like Canada are safer options.
Version 2. Residents decide driving and shorter trips, to places like Canada, are safer options.
Version 3. Residents decide driving, and shorter trips to places like Canada, are safer options.
Version 4. Residents decide driving and shorter trips to places like Canada are safer options.

My wife chose Version 4 alone.

Mark Nichol chose Version 3 and Version 4.

The correct answer is Version 2 and Version 4 (with Version 2 the more likely intended meaning).

Everyone agrees that Version 4 is correct; the questions are why does Mark erroneously think Version 3 is also correct and why does my wife fail to recognize that Version 2 is correct? Mark’s explanation supports my previous claim that among grammatically literate writers the most important comma errors derive from or at least implicate grammar errors. My grander claim is that comma errors create useless cognitive disfluencies, since they affect the reader’s grammatical parsing. In fields like brief writing, where the highest levels of clarity are advantageous, repeated comma errors—even if they’re subtle or controversial—summate to undermine Clarity.

Mark’s reasoning expresses a more straightforward error in grammatical analysis than the error I analyzed in The fundamental error of comma usage, as Mark claims that the string, and shorter trips to places like Canada, in Version 3, is an interjection, but an interjection (like Oh!) is grammatically isolated from the rest of the sentence. If the string were an interjection, the clause’s verb, are safer options, should be singular rather than plural. Since there’s no way to punctuate the sentence to make the verb singular, the italicized string, which must form part of its clause’s subject, can’t be an interjection.

But Version 2 is the correct answer if you’re allowed only one choice. The difference from Version 4  is that to places like Canada is a restrictive modifier in Version 4 and a descriptive modifier in Version 2, and the descriptive meaning is more probable. Read closely, Version 4 advises shorter Canadian trips, whereas the writer almost surely intended to advise limiting the length not just of trips to Canada (and similar places) but trips in general.