How to not write bad - Ben Yagoda 2013

Italics
How to not write wrong

A surprising number of people don’t realize that, in a text, italics or underlining indicate exactly the same thing. In typewriter days, it wasn’t possible to indicate italics, so we underlined for emphasis. Now that everybody writes on computers, underlining isn’t necessary, so don’t do it. Use italics, but only for emphasis, for titles of books and other compositions (as long as you’re consistent), to indicate words as words (as is done throughout this book), and for words in languages other than English. Putting a word in all capital letters is not an acceptable way to indicate any of these things, except in dialogue, where all-caps can suggest shouting at a very high volume, or, occasionally, in informal writing, where it can be amusing.

The foreign-language item demands some amplification. If a foreign word is familiar enough that readers will understand what it means—think joie de vivre, siesta, zeitgeist, espresso—don’t italicize it. However, sometimes you may have reason to use a more obscure foreign word or a short quotation from something said or written in a foreign language. Italicize the word or quote—and make sure you quickly translate it.

One complication with italics is e-mail. Some e-mail programs allow italicization, but others play dumb when you hit the appropriate keys, or instead give you a Spanish tilde sign or some other odd piece of punctuation. Some people compensate for this by using special cues for emphasis, like *this* or _this_ That’s okay for e-mail, but stay away for it in any other setting.