And why do we cling on to the redundant comma after the speech verb in direct speech: "She said, 'hello'". Aren't the inverted commas enough without the comma?
Why do we get tied into such knots? We'd like to blame the problem on the punctuation system that we've all inherited. Some people campaign for spelling reform but maybe it's time to agitate for punctuation reform. For example, just look at a question mark: ? It has two parts: a dot, and a squiggle. They always go together unthinkingly, like two sides of a coin, but there's no real reason why they should. In fact, there's a very good reason why they shouldn't: a question doesn't have to be the end of a sentence. The dot is just an ordinary full stop, so it signals the end of a sentence. Why shouldn't we have a comma there instead, then we'd be able to show that we haven't yet reached the end of a sentence? (There we go again - another awkwardly placed question mark. They really are a problem.) What we're campaigning for is a new punctuation mark, the "semi-question", consisting of a question squiggle on top of a comma - just like a semi-colon, in fact (hence the name). Here's the pattern: You use the semi-question at the end of a main clause which is a question but which is followed by other clauses in the same sentence. And while we're at it, what about the exclamation mark? What a pain sentences like this one are, because the punctuation can't stand next to the exclamation! We wanted the exclamation at the end of the first clause (after "are"). By the end of the sentence, it's lost its impact. The exclamation mark begins to feel twee and contrived.
Like all good revolutionaries, we have a Plan B. While we're waiting for the semiquestion and semi-exclamation to appear on our keyboards, we'll settle for an approach to teaching punctuation which emphasises the sheer creativity of the conventions. Let's stop linking it to breathing ("put a comma where you take a breath," we used to be told. Heaven help the asthmatics among us!). Instead punctuation is intrinsically linked to communicating shades of meaning in writing. To make this point, students might enjoy exploring the pipe-dream possibilities of inventing new forms of punctuation - as a way of reinforcing their understanding of the various dots and squiggles we use every day.
Richard Hudson is professor of linguistics at University College, London. Geoff Barton is headteacher of King Edward VI School, Bury St Edmunds, Suffolk