Yeah? So? First, it does not say that one must not use spaces around em dashes. Second, so what if it did? This is English we're talking about. The main rule of English is that there are no rules. If you want a rule for English: it's to speak and write in such a way as to be understood -- who would fail to understand the whitespace around an em dash?! Not I. But missing whitespace around an em dash can be confusing -- is that a compound? did the author mistype a hyphen? Ugly. Whitespace is nice. Use it.

There may not be rules but there are conventions.

These conventions are rarely very strict but they do help communicate your ideas. Understanding them and understanding the impact of not using them is an important set of knowledge if you want to be clear and well understood in your writing.

It is similar to good typography in that it isn't required but that it will often make the reader enjoy or understand the work more when reading.

Obviously there have been many great writers who knew how and why they were breaking those conventions. E. E. Cummings was a notable example.

I think you meant to write e e cummings.

It seems E. E. Cummings tended to prefer his name capitalized (though obviously he did not always follow consistent usage): https://en.wikipedia.org/wiki/E._E._Cummings#Name_and_capita...

You're saying only the qualified are allowed to break conventions you were taught. You are free to follow that; I am free to not.

Nothing about allowed there. It’s about communication & understanding.

You are free to break whatever convention you like. It will just effect your communication clarity.

Understanding that (and how and why too) will help you be more effective.

It’s no different to saying “you can program it that way if you want but understanding the conventions & methods other people use may help you have more readable and efficient code”.

Really. Whitespace around em dashes hurts my ability to communicate? Please explain.

How are you failing to understand "the reader will expect certain conventions so following those will make it easier to communicate effectively with them"?

This is not a hard concept to grasp.

The downvotes show the grammar nazis abound. I'm with Churchill, who famously said of not ending sentences with prepositions that "that is the sort of thing up with which I shall not put!".

There are rules to making oneself well- and easily-understood generally, and to appearing to be an educated writer to other educated people. If you care about neither of those things then sure, there are no rules.

Write like you talk, and usually you achieve both.

You can do it. Unless you have an editor, nobody is going to stop you. It just looks awkward and pretentious to anyone with knowledge of typographic conventions (as in pretending hard to be fancy while revealing your ignorance of standard practice.) It’s like using obscure words in an ungrammatical or unidiomatic way; again nobody but your editor is going to stop you, but anyone who knows the way those words are typically used will find it awkward.

Pretentious? Come on. There’s nothing inherently wrong with spacing your em dashes. It’s even part of the AP style guide.

I personally wrap them in thin spaces (U+2009), except in fixed‐width fonts, where I use an en dash with full spaces instead.

The AP is a poor source for a typographic style guide. They are a wire service not professional typographers, and my speculation is that their conventions come from a context of typewriter manuscripts rather than properly typeset books. They eschew en dashes and use hyphens to indicate ranges (e.g. 10-20 instead of 10–20) – something no professional typographer would condone – because they are expecting someone with a typewriter to only be able to type hyphens, whereupon the choice is either one hyphen or two. So in a manuscript you get spaces around pairs of hyphens -- like so -- standing in for dashes. Their style guide is designed so that someone doing the newspaper typesetting can directly copy the typewritten manuscript over to the press without thinking about what kind of dash to use.

In fixed-width fonts, do you literally use an en dash (U+2013) or do you use hyphen-minus (U+002D)?

I use UTF‐8 except when I have reason to stick to ASCII. (One such situation is public mailing lists, where people’s misconfigured mail clients constantly butcher any non‐ASCII characters when replying.)

No editor is going to tell you not to do something that lots of people do. As the other reply says, you're being a tad pretentious over nothing much. Chill.

In professionally typeset material people use either spaced en dashes – like this – or un-spaced em dashes—like this—but spaced em dashes are unconventional and unprofessional, frowned upon by anyone who knows what they’re doing. Sometimes professionals put hair spaces or thin spaces around em dashes — like this — but on the web those often are rendered improperly, such as on this forum. Try copy/pasting this paragraph into a rich text editor and swapping between a few typefaces to see what the effect should look like.