My writing instructors deride the “bad habit” of using semicolons; consequently, I have become accustomed to editing them out of my work.
Wow. A semicolon being a “big deal.” Well, I don’t think we can say the semicolon is lost.
Bumping this thread from almost 20 years ago the situation is getting even worse!
On the internet, semicolons have mostly been replaced with emoji. This is so desired now, that Discourse does the change automatically.
;) 
I suppose you could use the semicolon if you want half-assed writing.
The status of the interrobang is even more dire.
Some of us don’t use these new-fangled, flash in the pan gimmicks.
I’d rather see them not used than misused.
There is one on every Cat’s ass.
Wait. I thought that was an exclamation mark. 
This thread was revived just in time, says the First Dog on the Moon:
Today in “things that somehow made it past the copy editor”:
Perhaps, therefore, it will not be Vonnegart who wins out in the battle of the semicolon, but the rash, witty, louche Camille Desmoulins, as recreated by Hilary Mantel.
FWIW, pollster/pundit Nate Silver is doing his part to keep the semi-colon alive.
Just anecdotal, but: ISTM that instruction in “good writing” over – I don’t know – the past 50 years (?) has emphasized short, direct sentences. “Punchy” was an adjective attributed to this style of writing, and it was considered a very good thing. I’m sure many students (from late elementary to college) had their clever uses of semi-colons converted into two separate sentences in their teachers’ search for “punchy” writing.
Taking the 10-question semicolon quiz at the end of the article … ISTM, also, that many former uses of the semicolon are now commonly taken by dashes.
A semicolon has a different purpose than a colon, comma, or em-dash. It signifies a mid-sentence change of direction. A colon precedes a list, or indicates a clarification of what was said before the colon. Comma sets off a clause in the middle or at the end of a sentence, or separates the items in a list after a colon. An em-dash is an alternative to parantheses
I mostly use them as line termination indicators when making lists.
One;
Two;
Three.
Three licks.
I have a traumatic experience with the interrobang. No, seriously. It wasn’t the punctuation mark’s fault, though.
A semicolon can, more or less, be used in the same places as a period (though with slightly different meaning, of course). A dash can, more or less, be used in the same places as a comma. Rare are the cases where either a semicolon or a dash could be used grammatically.
There are a few places where a semicolon can be used in place of a comma, most notably for separating elements of a list where some of the list elements themselves contain commas. Otherwise, a sentence like “I’ve lived in Miami, Ohio, Indiana, Pennsylvania, and New York” could be ambiguous. But I don’t think I would use a dash in those cases.
I can use a semicolon properly - and a colon. My preference, however, is breaking a sentence into natural chunks, as I did in that first sentence. Dashes and parentheses are better for that, although commas can provide some of the work.
Where and how to break up long sentences has evolved over the years. A few hundred years ago commas were strewn like Johnny Appleseed tossing out apple seeds. Here’s an example from Addison and Steele’s The Tattler, from around 1710.
Letters from Venice say, the disappointment of their expectation to see his Danish Majesty, has very much disquieted the Court of Rome. Our last advices from Germany inform us, that the minister of Hanover has urged the council at Ratisbon to exert themselves in behalf of the common cause, and taken the liberty to say, that the dignity, the virtue, the prudence of his electoral highness, his master, were called to the head of their affairs in vain, if they thought fit to leave him naked of the proper means to make those excellences useful for the honour and safety of the Empire. They write from Berlin of the 13th, O.S., that the true design of General Fleming’s visit to that Court was, to insinuate, that it will be for the mutual interest of the King of Prussia and King Augustus to enter into a new alliance; but that the ministers of Prussia are not inclined to his sentiments. We hear from Vienna, that his Imperial Majesty has expressed great satisfaction in their high mightinesses having communicated to him the whole that has passed in the affair of a peace. Though there have been practices used by the agents of France, in all the Courts of Europe, to break the good understanding of the allies, they have had no other effect, but to make all the members concerned in the alliance, more doubtful of their safety from the great offers of the enemy. The Empire is roused by this alarm, and the frontiers of all the French dominions are in danger of being insulted the ensuing campaign: advices from all parts confirm, that it is impossible for France to find a way to obtain so much credit, as to gain any one potentate of the allies, or make any hope for safety from other prospects.
We no longer put commas before “that”. Other commas would be excised by any contemporary editor. The word “advices” is obsolete, at least in American writing. The semicolon and the colon would be reversed today. There are six sentences that comprise a 305 word paragraph. Navigating them requires Dramamine.
I think reading comprehension is greatly increased in modern popular writing. Older rules and styles have been superseded - and properly so. The language and its expression changes regularly and will - and should - continue to do so. That’s not to say that every alteration is an improvement, but the change is extremely positive overall.
A semicolon would not have been properly used in place of that dash.
Maybe.
As a reader however my preference is having a variety of sentence lengths and forms. Every sentence being terse gets tedious, as tedious as a run on sentence can be. Some pairs of ideas that could be written as separate sentences read better, IMHO, connected by a semicolon. It is a different function than a dash.
FWIW writing with grammatic complexity and idea density in early life has correlated with less dementia risk during later aging. Semicolons properly used are part of grammatic complexity and likely also correlate with idea density.
https://jamanetwork.com/journals/jama/article-abstract/396775
So use your semicolons as part of preventative health!
As it happens, I was reading a poetry textbook yesterday (Donne). The editor explained that he had replaced commas with semi-colons where he thought Donne really needed it, because the intention of this particular edition was to make the poetry readable to a modern (20th century) student, and at the time Donne was writing, a comma would be used everywhere: for a long, or very long, pause or break.