Stop or I'll punctuate!

Idly language-linking here and there, I recently discovered that the most famous punctuation book of all time has not just a website but also an interactive quiz. Naturally, I couldn't resist.

It's only 12 questions, the first six on apostrophes and as straightforward as apostrophe questions can be. You click to add punctuation, as needed, to expressions like "the children's hands" and "four yards' worth."

The next six, on commas, are more complicated. "Stop, or I'll scream"? The quiz demands the comma, but does it really belong in that short, urgent command? When I check the book, I see the problem: Truss thinks "Stop" is an interjection, like "blimey" or "golly" or "heh-heh." But it's not -- it's a verb. And in a short compound sentence like "Stop or I'll scream," that comma is absolutely optional.

Then there's this puzzler:

Of course there weren't enough tickets to go round.

The test wants a comma after "of course." But for me, the punctuation would depend on what that "of course" is meant to do. And in the sample sentence, it's very hard to guess. The "of course" might be emphatic:

"Of course there weren't enough tickets to go round -- he always forgets to buy me one."

Or it might be parenthetical:

Jane gave us six tickets. Of course, there weren't enough tickets to go round, but we knew not everyone would want to see the play.

In the first case, the comma digs a pothole in the rhythm; in the second one, it's natural.

Oddly enough, in the book this test sentence is used to illustrate "weak interruptions" (like "of course") that don't always require commas: Truss says she, and you, can go either way.

Skipping the commas may drop your score down to "75 percent stickler," but that doesn't mean you're not 100 percent correct.