Best shown by example:
(From Haruki Murakami's The Wind-Up Bird Chronicle)
"But I still felt bad," she went on. "So I dragged myself all the way to your house later--like an idiot.
"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?