Punctuation!

 Grammar manuals can be entertaining.  Mine tells me the exclamation point is used to indicate deep emotion and should be avoided.   In short, here is a tool but don't use it.

That is a wonderfully dry example of how grammar advice can contradict itself. The exclamation point is a bit like a spice in cooking: the existence of a strong flavoring does not mean every dish should contain it, but banning it entirely would be silly.

Older style manuals often took that approach because formal writing was expected to be restrained. The exclamation point was associated with shouting, melodrama, or advertising: “Amazing! Incredible! Buy now!” So the advice became, essentially, “Use it only when absolutely necessary,” which in practice often became “avoid it.”

But there are perfectly legitimate uses. It can mark genuine surprise, alarm, delight, humor, or a sudden interruption:

    “Look out!”

    “You won!”

    “I never expected that!”

The real issue is not the mark itself but whether the emotion is earned. A paragraph full of exclamation points tends to flatten them all out—if everything is exciting, nothing is. One well-placed “!” can have much more effect than five of them.

It is also amusing that the exclamation point has such a long history of being treated as a dangerous object. Some style guides have even joked that it is the “punctuation mark most likely to embarrass its user.” Yet writers from Dickens to modern novelists have used it effectively.

Your manual’s wording is a classic example of prescriptive grammar: “Here is a tool; now, please demonstrate your wisdom by resisting the temptation to use it.” A bit like giving someone a fire extinguisher and adding, “But really, try not to have fires.” 😄

To be frank, I would not use it in the examples you provide.  The words themselves convey the idea and it is therefore redundant.  

That is a very defensible writer’s instinct, and it gets at the deeper reason many experienced editors are suspicious of the exclamation point: the sentence should usually carry the emotion, not the punctuation.

Your examples are good cases. Compare:

    “Look out!”

    “Look out.”

The first suggests urgency, but the words themselves already do the work. Context supplies the rest. If someone is standing in the path of a falling object, the period does not make the warning less urgent.

Similarly:

    “You won!”

    “You won.”

The difference is less about the fact and more about the narrator’s attitude. The exclamation point tells the reader, “This is exciting.” A strong writer often prefers to let the reader experience that excitement without being instructed.

There are places where the mark does add something, especially where the words alone could be ambiguous:

    “You did it!” (joy, amazement, disbelief)

    “You did it.” (could be praise, accusation, or simple information)

Even there, a skilled writer can often find another way:

    “You did it,” she said, staring at the finished work.

The description replaces the punctuation.

The amusing thing is that this view is very close to what many old grammar manuals were trying—sometimes clumsily—to teach. They were not really saying “the exclamation point is forbidden”; they were saying, “Do not use punctuation as a substitute for writing.” A sentence that needs an exclamation point to become exciting may not have been very exciting to begin with.

The em dash is an interesting case because it is both genuinely useful and genuinely overused. Your observation about keyboards is also historically accurate: unlike the hyphen, it was never treated as an everyday character, so many writers either had to know a special key combination or simply used a pair of hyphens (--) instead.

The traditional advice to avoid it came from much the same school of thought as the caution about exclamation points: punctuation should not become a substitute for structure. The em dash is very tempting because it can do almost anything:

    replace a comma,

    replace parentheses,

    replace a colon,

    create a dramatic pause,

    interrupt a thought,

    add an aside.

That versatility is precisely the problem. A writer who discovers the em dash can start sprinkling it everywhere.

Compare:

    The meeting—which had already lasted three hours—finally ended.

versus:

    The meeting, which had already lasted three hours, finally ended.

The first gives the aside more emphasis. The second simply provides information. Neither is wrong, but the dash makes the writer say, "Pay attention to this."

Where I think the em dash earns its keep is in places where there is a genuine break in thought:

    I was prepared to agree with him—until I read the last paragraph.

A comma would not capture the reversal, and a period would be too abrupt.

It is also excellent for comic timing:

    He had only one goal in life—to become famous for doing nothing.

The pause is part of the joke.

But I suspect your objection is similar to your objection to unnecessary exclamation points: many writers use the mark to announce emphasis instead of creating it. A sentence with three em dashes often feels like a person who keeps tapping the microphone to make sure everyone is listening.

Interestingly, some of the most elegant prose uses very little punctuation beyond periods and commas. The great trick is that the rhythm comes from the words and sentence structure, not from increasingly elaborate road signs placed along the way. The punctuation should guide the traffic, not become the scenery.

I was prepared to agree with him until I read the last paragraph.

Exactly. And your version is arguably the stronger one.

    I was prepared to agree with him until I read the last paragraph.

The sentence already contains the turn. The word “until” does the structural work: it tells the reader that the first expectation was interrupted by a later discovery. The em dash merely draws attention to something the grammar has already made clear.

The two versions create slightly different effects:

    I was prepared to agree with him until I read the last paragraph.

This is calm, almost analytical. It lets the reader discover the change of mind.

    I was prepared to agree with him—until I read the last paragraph.

This is more theatrical. It says, “Here comes the important reversal.” It is closer to spoken emphasis, where a person might pause before delivering the punchline.

Neither is wrong, but your instinct reflects a broader principle: if the words already create the rhythm, extra punctuation can be noise. The dash is not adding meaning; it is adding performance.

This is probably why many older style guides were suspicious of it. A careful writer can use an em dash beautifully, but it is a very easy tool to overuse because it gives immediate dramatic effect. It is the literary equivalent of turning up the volume when a better speaker might simply choose better words.

I will say this, the em dash does tend to beat parentheses:  I was prepared to agree with him (until I read the last paragraph).  Horrible.  Parentheses do what the style manuals accuse the em dash of doing, break the thought.  Also, it has to be closed, adding to the end of sentence mess of marks English has gotten itself into.

That is a good distinction. The em dash and parentheses are often grouped together because both can set off an interruption, but they create very different relationships between the main sentence and the aside.

Your example is a good illustration:

    I was prepared to agree with him (until I read the last paragraph).

The parentheses make the ending feel like an afterthought—almost as though the writer is saying, “Oh, and one minor additional detail...” But the detail is not minor; it is the entire reason the speaker changed his mind. The punctuation has accidentally downgraded the important part of the sentence.

The em dash version:

    I was prepared to agree with him—until I read the last paragraph.

at least acknowledges that the second part is central. It says, “Here is the point where the situation changes.”

Parentheses are at their best when the material really is optional:

    The conference will be held in June (the exact date has not yet been announced).

Remove the parenthetical and the sentence still functions. The information is genuinely secondary.

You also touch on one of English punctuation’s less elegant features: the pile-up at the end of a sentence. Parentheses can create some awkward-looking combinations:

    Did he really say that (or was I mistaken)?

    She asked, “Are we finished?”

English has inherited a lot of punctuation conventions from different eras, and they do not always combine gracefully. The rules are mostly logical, but the visual result can sometimes look like the punctuation marks are having a small argument at the edge of the sentence.

There is also an interesting historical irony here: the em dash was once the more common solution for interruptions. Parentheses came to be favored in some formal writing because they were seen as tidier and more restrained. Then the em dash made a comeback, especially in modern journalism and informal nonfiction, partly because writers wanted a way to create emphasis without the visual barrier of parentheses.

Your preference is really a preference for keeping the reader inside the sentence. Parentheses step outside and whisper something to the reader; an em dash keeps the interruption on the same stage. Sometimes that is exactly the right effect. Sometimes, as you suggest, the best answer is neither—just write the sentence so it does not need the interruption at all.