Three decades ago, when I was doing some contract work for a software company that shall go nameless, a co-worker suggested an optional plug-in for their flagship product. For a mere $5000.00, a customer could install a module that would automatically turn two spaces into one any time that one of their users typed two consecutive spaces (whether inadvertently or intentionally). Having taken a typesetting/typography course a few years earlier, I became thoroughly convinced that the two-spaces habit was just a holdover from the typewriter age and was therefore unequivocally wrong when doing word processing or other computerized typesetting. I still am. It simply looks amateurish, as no professional publications ever use two spaces after a period. So why do so many people still use two spaces? That’s easy: either they are old enough to have learned on a typewriter (where the correct thing was to use two spaces, because of the lack of proportional spacing) or else they were taught by someone who used a typewriter. Or perhaps they were taught by someone who was in turn taught by someone who used a typewriter.
So putting two spaces after a period is just plain wrong. It can’t be a matter of opinion; it’s just wrong.
I was confirmed in this view by reading The Mac is not a Typewriter, by Robin Williams. (No, not that Robin Williams.) She also had a companion volume, The PC is not a Typewriter, but that got much less attention; back in the ’80s, PC users were assumed not to care about how things look.
But now I see that the situation is actually a bit more nuanced than that. The link in the preceding sentence reminded me that the aforementioned-software-company-that-shall-not-be-named provided no less than seven sizes of spaces, thereby affording more choices than the traditional one space or two. Most of us are stuck with the “crude tools” mentioned in the link, and therefore have to choose. The author of the linked article cops out by saying this:
[T]he bottom line is clear—you can use either one or two spaces after periods, if you are using crude tools (like Microsoft Word, WordPress, or Google docs) that don’t have good handling of sentence-ending spacing built-in.
Maybe so. But I still claim that using two spaces is wrong.