Differentiating comma/period use in mid-dialogue

Question

Best shown by example:

(From Haruki Murakami's The Wind-Up Bird Chronicle)

1. "But I still felt bad," she went on. "So I dragged myself all the way to your house later--like an idiot.

2. "Don't worry," I said, "she's not cuckoo. Different people have different tastes."

Now you see how in (1), the line is interrupted by "she went on", which is delineated by a period and the dialogue continues with a capitalization. And in (2), "I said" is concluded with a comma, and the dialogue continues with no capitalization. I can't understand the difference. Is there a rule regarding this, or is it a stylistic choice depending how you want the sentence to sound in the reader's head?

It isn't as simple as 'in the first example, "But I still felt bad" is a complete sentence, whereas in the second example "Don't worry" is only the beginning of a longer sentence.'

The reason I say it is not that simple is that both examples could have been either one sentence or two. "Don't worry" could easily be its own sentence, just as "But I still felt bad" could be the comma'd opening clause of a longer sentence.

So does that make it a stylistic choice?

Answer 1

As I understand things, you place a comma after the interruption if the first quotation was not a complete sentence, and a period if it was. The rule really is as simple as you inferred. The stylistic element comes in where you have to decide how you would punctuate a quotation if it wasn't to be broken.

By example:

"My most worthy adversary, we meet again," becomes, " 'My most worthy adversary,' the villain scoffed, [comma] 'we meet again.' "

Whereas

"My most worthy adversary. We meet again," becomes, " 'My most worthy adversary,' the villain scoffed. [period] 'We meet again.' "

Answer 2

You would place a comma after the interruption if the first quotation was not a complete sentence, but dialogue doesn't have to use complete sentences. Using the period in sentence 1 amounts to deciding not to use complete sentences within the dialogue.