[1][2][3] Houston, in his book, Shady Characters: The Secret Life of Punctuation, Symbols, and Other Typographical Marks, suggests that the demise of this form of punctuation may be due to the emergence of hostile style guides: The Chicago Manual of Style, launched in 1906, ruled against the dash hybrids from the start—except, curiously enough, the stop-dash, which was permitted only to introduce notes or asides, as in the construction "NOTE.—", though this too had been expunged by the 1969 edition.
"A note in Mechanical Translation and Computational Linguistics, volumes 4–5 (1957) indicates that compound points were not altogether unheard of even at that date:[4] The present analysis will include all those punctuational patterns which are commonly found in normal technical language.
"Wolsey's return to power was discussed openly as a probability,—a result which Ann Boleyn never ceased to fear.
As print broker Robert Charles Lee stated: "The idea is to impart the feeling that the narrator is like pointing a finger in a determined manner at 'this thing' under discussion.
"[citation needed] What seemed fundamental to good reading in 1839 seemed superfluous to critics less than a century later, at least in the case of comma-dash combinations.
The object of adding two marks is to widen the separation; but there is no utility in this, for the comma, dash, and parenthesis perform, mainly, the same office, the enclosing of expressions that might be left out and the sense of the sentence be complete.
Each represents a greater degree of separation, in the order named, so that, if the dash be not strong enough, the parenthesis may be used.The continued use of compound points eventually fell into doubt, especially as the timing theory of proper punctuation began losing ground to the sense argument.