A difficult part of writing for me is when a single sentence–especially dialogue–contains two tones. It sounds best as a single sentence, but ending with a period, or alternative punctuation, looks wrong. As well as this, using two sentences also looks wrong.
I can’t think of a great example right now, but I know I’ve wanted punctuation that doesn’t exist before. I’ve had moments where it would have been so useful to have a “;!” and a “;?” mark.
IIRC “something so damned simple” is a fragment or dependent clause, unless “[it is]” was somehow implied, in which case an em dash may be more appropriate. A simple comma might also suffice, since the clause modifies “this” from the next phrase.
You’re correct, I think you could use an em dash to better effect if you wanted to keep the original order. You could also use a semicolon or even just leave it as a sentence fragment as a stylistic choice. There are many, many ways that someone could structure a sentence.
I think in any situation in which a new type of punctuation seems sensible you would be better served by rewriting the passage instead, but conceptually I’d be interested in seeing a new punctuation mark gain popularity just to see what it would be used for. The idea itself isn’t a bad one.
Agreed, the virtue of a living language is change. I don’t always agree with the change but over time it makes language more expressive. A recent example is the word aesthetic used as a standalone adjective, as in “that’s so aesthetic.” While it strikes me as painfully meaningless — which aesthetic? — it’s common enough now to have been widely adopted as a general marketing term. That’s become an accepted use of the word, and so be it. I’d welcome the ability to more easily indicate tonal shift inside sentences, the way we do verbally. Just need it to become popularized enough.