[found on the-word-blog.com; by Heather]

“The Rule (According to CMS 6.3): Punctuation should appear in the same font or typeface as the general body text of a document. So if you have a roman sentence that contains an italicized word followed by a comma, the comma should appear in roman.”

To read Heather explain about the exceptions to this rule, click HERE.

[Found on http://the-word-blog.com/2009/04/28/formatting-ink-italics-punctuation/]