The MHRA Style Guide Online
A Handbook for Authors and Editors • Third Edition
From Chapter 5, 'Punctuation'
5.5 Punctuation with Italics
There are italic forms of most marks of punctuation. The type style (roman or italics) of the main part of any sentence will govern the style of the punctuation marks within or concluding it. If the main part of a sentence is in roman but an italic word within it immediately precedes a mark of punctuation, that mark will normally be in roman. However, if the punctuation mark occurs within a phrase or title which is entirely in italics, or if the punctuation mark belongs to the phrase in italics rather than to the sentence as a whole, the punctuation mark will be in italics:
Where is a storm more brilliantly portrayed than in Conrad’s Typhoon?
In Edmund Ironside; or, War Hath Made All Friends, a play that survives in manuscript, we see this technique in operation.
Kingsley followed this with Westward Ho!, perhaps his best-known novel.
Who wrote Who’s Afraid of Virginia Woolf??
Do not follow the practice of substituting roman for italics in titles within italicized titles (e.g. Understanding Les Fleurs du mal: Critical Readings); in such cases, quotation marks should be used even if they do not figure in the original, e.g. Understanding ‘Les Fleurs du mal’: Critical Readings.