“Not to use a mark of exclamation is sometimes wrong: How they laughed., instead of How they laughed!, is not English. Excessive use of exclamation marks is, like that of italics, one of the things that betray the uneducated or unpracticed writer: you surprise me, How dare you?, Don’t tell such lies, are mere statement, question, and command, not converted into exclamations by the fact that those who say them are excited, nor to be decorated into You surprise me!, How dare you!, Don’t tell such lies!. It is, indeed, stated in a well-known grammar that ‘A note of exclamation is used after words or sentences which express emotion’, with, as example, How are the mighty fallen in the midst of the battle! I am distressed for thee, my brother Jonathan!. The second half of this quotation clearly violates the rule laid down above, being, however full of emotion, a simple statement, and yet having an exclamation mark. But anyone who will refer to 2 Samuel i. 26 will find that mark to be not the Bible’s, but the grammarian’s; the earlier one of verse 25 is right. So far, the inference seems obvious and simple — to confine the exclamation to what grammar recognizes as exclamations, and refuse it to statements, questions, and commands…
Though a sentence is not to be exclamation-marked to show that it has the excited tone that its contents imply, it may and sometimes must be so marked to convey that the tone is not merely what would be natural to the words themselves, but is that suitable to scornful quotation, to the unexpected, the amusing, the disgusting, or something that needs the comment of special intonation to secure that the words shall be taken as they are meant. So: You thought it didn’t matter!, He learnt at last that the enemy was — himself!, Each is as bad as the other, only more so!, He puts his knife in his mouth!. But not: That is a lie!… Who cares!, I wish you would be quiet!, Beggars must not be choosers!; in all these the words themselves suffice to show the tone, and the exclamation mark shows only that the writer does not know his business.”
From the section “Exclamation” in H.W. Fowler’s A Dictionary of Modern English Usage, first published in 1926. The book has just been reprinted as part of the Oxford World Classics series and may be worth picking up for that strange someone in your life who’s into this sort of thing.