Updated May 2020, because internet.
There are some punctuation marks that can make prose look absurd — especially with overuse. Scare quotes and exclamation marks are two of the most abused. Here are simple tests you can use to decide where they should appear in your own writing.
These are used to indicate quoted words, spoken or written. Standard styles do not use quote marks to indicate that a word is a term. Italics are used for this, and only sparingly. When they are used to indicate something besides a direct quote — and you’ll have to tell me what that “something” is — they’re called scare quotes.
[CMOS 7.55] “Scare quotes”. Quotation marks are often used to alert readers that a term is used in a nonstandard (or slang), ironic, or other special sense. Nicknamed scare quotes, they imply, “This is not my term” or “This is not how the term is usually applied.” Like any such device, scare quotes lose their force and irritate readers if overused.
How to “decide”
Make “air quotes” every time you want to put a word or phrase in quotation marks. When you start to get carpal tunnel syndrome from “acting them out,” go back and “reassess” your “choices.”
If you really do want to indicate the unusual use of a term, do it once, then set it without the scare quotes. “Please.”
These should be reserved for actual instances of outrage or exuberance. (Except as we pass 2020… See below.)
[CMOS 6.71] An exclamation point (which should be used sparingly to be effective) marks an outcry or an emphatic or ironic comment.
[CP, 386–7] Do not overuse this strong mark of punctuation. Use it to denote great surprise, a command, deep emotion, emphasis and sarcasm. … Do not use an exclamation mark to end a mildly exclamatory sentence.
How to decide!
Each time you use an exclamation mark, leap in the air with pompoms.
Feel right? Go ahead and use it!
Feel silly? Use a period instead.
Here’s the cool thing about language: it changes! And the way it changes (in English) is dictated by those actually using the language, not some panel of gatekeepers. When it comes to exclamation marks, I have been convinced that their use has morphed since I wrote the OP six years ago. They are now used (especially in informal contexts such as internet comments, texting, and friendly emails) to express:
In fact, some suggest that a single exclamation mark no longer conveys enthusiasm at all. Two, or even three, are required at once!!!
Exclamation marks are friendly; periods are angry. I feel like kids today are smelling colours! I’m in; I want a taste, too!
What about negative statements? Does an exclamation mark on a negative statement still sound like yelling or are they a friendly pat on the back? You tell me.
Stalwarts claim that exclamation marks still have no place in more formal writing; the words should convey the emotion, not the punctuation. And what IS formal writing? Workplace emails don’t seem to count, at least among peers. Just because a book takes a well substantiated look at a subject, does it have to be written in a “formal” tone? Perhaps it will reach more readers by using a friendly sprinkling of exclamation marks.
And if we do accept them in our more formal writing, is there a limit to how many we can use before they become meaningless or absurd? When does the writing move from friendly to excited puppy? You tell me!
“Because internet” in the update note is both an acknowledgement of the influence of the greatest medium for print yet invented (and the medium ruled by the masses rather than publishing gatekeepers) and a nod to the title of the 2019 book by Gretchen McCulloch. For a short glimpse at this linguistic argument/observation, check out this 2018 article.
Photo by Peter MacKinnon used under CC BY-2.0 license.