When you italicize a whole sentence, do you italicize the period at the end, too?I come from the newspaper side of the publishing business. Newspapers have a long tradition of ignoring the italics option entirely, rooted in the days when printing presses didn't have italic fonts. So I'm none too swift on the italics issue. (And don't get me started on en dashes.) I checked the AP Stylebook — a newspaper-centric resource — and came up empty-handed.
Then I checked the Chicago Manual of Style, which is far more italics-friendly. Still. Bubkes. Chicago did have a passage on how to deal with possessives of italics. Do not, Chicago says, italicize the S.
Gone With the Wind's message is clear.
That S is not italicized, per Chicago.
Then, when faced with the option of digging further on behalf of someone else's 15-year-old, I was confronted by my own 2-year-old (cat, that is). The hardest question he's ever posed to me is, Will you please throw this soccer ball?
And that's when I put down the books.
Since then, Janet has found the passages in Chicago. She posted them as a comment, but for those whose settings don't automatically show comments, here's Janet's contribution. Thanks, Janet!
CMS 15th ed., section 6.3:
"Punctuation and font: primary system. All punctuation marks should appear in the same font---roman or italic---as the main or surrounding text, except for punctuation that belongs to a title or an exclamation in a different font. This departure from Chicago's former usage serves both simplicity and logic. For parentheses and brackets, see 6.6. for an alternative system, see 6.5."
"Punctuation and font: alternative system. According to a more traditional system, periods, commas, colons, and semicolons should appear in a the same font as the word, letter, character, or symbol immediately preceding them if different from that of the main or surrounding text. ... Question marks and exclamation points, however, should appear in the same font as the immediately preceding word only if they belong to a title or an exclamation."
In short, you can go either way, but italicizing the period is the latest recommendation