In most cases, the emdash is used symmetrically to add Parenthetical Details.
It can also be used unsymmetrically to add Details at the end of a sentence.
[[ EDITORIAL COMMENT :
This Question is about "2 Single Emdashes" Versus "1 Double Emdash" ; It is not about the spacing around the Emdash ; It is common not to use spaces , but it is Possible to use spaces according to some Style Guides.
Eg 1 :
Most grammar resources and style guides advise not to put any spaces before or after an em dash [....] other style guides and many newspapers will often put a single space before and after an em dash
Eg 2 :
The em dash is typically used without spaces on either side, [....] Most newspapers, however, set the em dash off with a single space on each side.
I have included Examples with and without spaces. The Crux of this Post is the quote by Jimmy Wales, not my Examples.
Here is this Grammarly Article which might be relevant :
END COMMENT ]]
Symmetrically Parsed Example:
It turned out that the three sisters ( Alexa, Siri, and Cortana ) were actually robots.
It turned out that the three sisters — Alexa, Siri, and Cortana — were actually robots.
When I gave away the oxen (all 8 of them) I had more time to travel.
When I gave away the oxen—all 8 of them—I had more time to travel.
Unsymmetrically Parsed Example:
The winner was the last : Cortana.
The winner was the last — Cortana.
The verdict was shocking : Guilty !
The verdict was shocking—Guilty !
Now, confusion arises when these two uses get mixed up in the same sentence.
I've joked many times — it may not be a great business model to give things away and hope people will voluntarily support them — but this is how I've built my career so far!
SOURCE (including the spaces) :
Problem : It looks like the Symmetric use, but it is actually the Double use of the Unsymmetric use !
It can be interpreted in both ways !
I've joked many times [that] "It may not be a great business model to give things away and hope people will voluntarily support them" but this is how I've built my career so far!
Meaning : Jimmy has built the career by joking many times ! The Joke is not all that funny !
I've joked many times — "It may not be a great business model to give things away and hope people will voluntarily support them — but this is how I've built my career so far!"
Meaning : Jimmy has joked many times ! The joke is still not all that funny !
(1) Is my thinking correct or valid ?
(2) In general, is there a way to remove the ambiguity without using more Punctuation like Parenthesis or Quotes ? Eg: By varying the size of the Dashes or the Spacing ? In a nutshell, can we indicate that Double emdashes in sentence are either indeed Symmetrical or indeed unsymmetrical ? Or is it inherently ambiguous ?