Reader Question: Comma Use

A good question from a reader:

My name is Rishi, and I am a college student who is very interested in learning how to write grammatically-error-free prose. It is a tall order, but your blog (and articles in Writer’s magazine) have been very helpful teaching aids. I was introduced to your blog by way of the Grammar Girl’s website. After noticing that many of articles appearing on her site were guest written by you, I clicked on the link to your blog -- and have been hooked since.

I was wondering if you could please help me with this question: Why do many clauses that begin with the phrase “and that” have a comma in front of the conjunction “and?” Take, for instance, the sentence: “I wish it were raining a lot right now, and that the wind would blow fiercely more often.” I understand that a comma (and a conjunction) needs to be inserted between two independent clauses, but it seems to me that the second part of the sentence – which begins with the phrase “and that” – is not an independent clause. After all, we would never use the expression “and that the wind blows fiercely more often” in a stand-alone manner. I wonder, then, why is it that clauses of this sort have a comma inserted in front of them?

I would be very grateful for your insight, Ms. Trenga, and many thanks for your time.

With gratitude,
Rishi

p.s.: I hope that I have not committed an egregious number of grammatical errors in this email!

Rishi is right about commas and independent clauses. If you go by that rule, a comma before "and that" would not work. But... commas also indicate a pause, and if you have a long sentence, a comma can help the reader pause in the right place, so my view is that a comma would be acceptable in a long sentence. If, on the other hand, you have a somewhat short sentence like "I like it that you smile and that you laugh" then a comma would not be necessary.

Thanks, Rishi, for the question, and no, your e-mail message was not full of egregious errors!