Em-dashes: with or without spaces

[frivoal]

On the one hand, according to both the Chicago Manual of Style and The Gregg Reference Manual, em dashes should be used without spaces on either side. And the W3C Manual of Style calls for respecting these references when it comes to punctuation.

On the other hand, or tag line is now “W3C's mission is to make the web work — for everyone” (with spaces), and the Team wants this punctuation / spacing respected.

Is that an exception? Is that a sign that the W3C Manual of Style should recommend an exception to the Chicago Manual of Style and The Gregg Reference Manual on this topic?

In addition to stylistic preferences, I'll note that there's a certain amount of assumptions (for a lack of spaces) built into tooling. For instance, that's how bikeshed generates them, and from there, that's how a lot of existing content is typeset. If we do want to change, that's not necessarily a show stopper, but I thought I'd point it out.

[plehegar]

I believe that the Manual of Style only applies to W3C Technical Reports and creating exceptions based on documents that are outside the scope of the manual of style (eg w3.org/mission) doesn't seem a sustainable approach to me. If a TR document wishes to quote the W3C mission, then it should respect the original text, as recommended by the Chicago Manual of Style.