I'm especially fond of Joseph Moxon's _Mechanic Exercises on the Whole Art of Printing_ (1683-4), as revised and reprinted by the Oxford University Press (1958).
This work makes it clear that most of our "pointing" (punctuation) was developed by printers and proof-readers to indicate the length of pauses that seem to meke the best sense when reading text aloud, and originally was, to put it bluntly, arbitrary and artificial, being only remotely related to grammatical construction. So yes, the whole field is highly subjective. As new mediums have been introduced -- lead type, the mechanical typewriter, electronic fomats -- changes have taken place, & will continue to do so, giving people who like to quibble much opportunity to indulge in this practice, and in pontification.
As a member of The Typewriter Generation, I interpret the ordinary dash (also serving as a hyphen or a minus sign) as being an en-dash, so two are used to create an em-dash (with a blank space on either side) as indicating a longish pause to set off a word or phrase that isn't quite remote enough from the context to deserve the use of the parenthesis. I'd try not to use this in Formal Writing... but then, I've not done any really Formal Writing in many decades.
no subject
This work makes it clear that most of our "pointing" (punctuation) was developed by printers and proof-readers to indicate the length of pauses that seem to meke the best sense when reading text aloud, and originally was, to put it bluntly, arbitrary and artificial, being only remotely related to grammatical construction. So yes, the whole field is highly subjective. As new mediums have been introduced -- lead type, the mechanical typewriter, electronic fomats -- changes have taken place, & will continue to do so, giving people who like to quibble much opportunity to indulge in this practice, and in pontification.
As a member of The Typewriter Generation, I interpret the ordinary dash (also serving as a hyphen or a minus sign) as being an en-dash, so two are used to create an em-dash (with a blank space on either side) as indicating a longish pause to set off a word or phrase that isn't quite remote enough from the context to deserve the use of the parenthesis. I'd try not to use this in Formal Writing... but then, I've not done any really Formal Writing in many decades.