Back when I was in high school I forced my way into the typing class. You see, I was in the Arts and Sciences stream, and why would anybody but girls in Business and Commerce need to know how to type?
While in typing, we were taught to put two spaces after any punctuation with a dot in it: periods, colons, question marks, and exclamation marks. One space everywhere else. This it is and has always been.
Times have changed. The new standard is one space everywhere, and editors get really cranky if you make them search-and-replace your entire document to get rid of double spaces.
I’ve seen various online discussions about the one/two space rule, and it’s amazing how many people either (a) complain that it’s really difficult to change, or (b) refuse to change because they refuse to change.
I’m lazy, so I solved the whole problem once and for all.
In LibreOffice, go to Tools -> AutoCorrect -> AutoCorrect Options -> Options. Check “ignore double spaces.” Now you can type as many spaces as you want and it will only show one.
What if you repeat a space while cutting and pasting? Make sure the rule Tools -> LanguageTool -> LanguageTool -> Options -> Typography -> Whitespace Repetition is checked. That will show you everywhere that multiple spaces sneaked through the AutoCorrect check.
That’s it. Most double spaces will be prevented, and the rest will show up during grammar checking.