6: Punctuation
6.18: Commas relative to parentheses and brackets
When the context calls for a comma at the end of material in parentheses or brackets, the comma should follow the closing parenthesis or bracket. A comma never precedes a closing parenthesis. (For its rare appearance before an opening parenthesis, see the examples in 6.129.) Rarely, a comma may appear inside and immediately before a closing bracket as part of an editorial interpolation (as in the last example; see also 13.59).
After several drummers had tried out for the part (the last having destroyed the kit), the band decided that a drum machine was their steadiest option.
Her delivery, especially when she would turn to address the audience (almost as if to spot a long-lost friend), was universally praised.
“Conrad told his assistant [Martin], who was clearly exhausted, to rest.”
“The contents of the vault included fennel seeds, tweezers, [straight-edged razors,] and empty Coca-Cola cans.”
Here are a few comments from the CMOS forum. These examples should help this rule stick in your mind!
• I went to Bob’s (he didn’t realize I was on my way) and caught him kissing my girlfriend.
Lowercase “he” and exclude the period at the end of the sentence within parens? Is this correctly punctuated?
• I told Mary (does she think I’m stupid?) that I was aware of the affair.
Lowercase “does” and use the question mark within parens? Is this correctly punctuated?
• Joe may apologize (he is such a creep!) for the affair.
Lowercase “he” and can I use the exclamation point within parens? Is this correctly punctuated?
I think that the only terminal punctuation that is omitted in parens is the period. The question mark and exclamation mark, I believe, are the only ones that can be used at the end of a sentence within parens.