I learned two spaces in typing class. I think having two spaces after the period looks better and makes more sense, both in fixed-width fonts and in variable-width fonts. I've never heard an argument against it that wasn't based on incorrect premises ("You don't need to do that anymore! It looks fine without it!" Well, no it doesn't look fine without it, so yes, I'm going to keep doing it.)
But yeah, it's weird the effects of backwards compatibility... so many things decided 40 years ago, which we can't change because it would break someone's configuration.
Googling the question right now, there are two recent developments I was unaware of. There’s a 2018 paper [1] about it showing no perceptual benefit to either spacing, and also in 2020 MS Word changed their spelling checker to consider 2 spaces an error [2]. This second article tells the opposite story from what I thought I’d heard (but maybe this is what I was thinking of) - it says 2 spaces were developed for monospaced typewriters, and not for print.
Your summary of the 2018 paper was incorrect. They found it made no difference to people who typed 1 space. People who typed 2 spaces read 2 spaced text 3% faster with equal comprehension. And the limitations were significant. The subjects were young and had normal or corrected to normal vision. The task was reading paragraphs in order. And I did not see periods inside sentences mentioned.
The way I see it, if some typesetting system thinks one space looks better than two and renders two as one anyway, or if the difference is otherwise imperceptible, then there's still no reason for me to stop using two. It's pure muscle memory and if people can't tell the difference then I'm not going to stop.
Sounds good to me. I wonder if your comment was intended to respond to the sibling comment to mine? Anyway, I’d agree there’s no reason to stop, and anyway 2 spaces has been the rule and still is for some people. Language and technology being fluid is why there’s debate and why the number of spaces has changed over time, and it’s also why it’s okay to do it the way you want to.
Do you think pretty much the entire web looks awful then? Because HTML rendering collapses whitespace by default. Your comment renders with only a single space after the period, despite the fact that you typed 2.
See, this is the attitude I don't understand. I'm not going around adding extra spaces after your periods; why are you so intent on removing mine? Who appointed you the textual aesthetics police? Let people add spaces according to what they think looks best, and the thing most people prefer will win out.
Feel free to add spaces, I’m just glad I don’t see them. I don’t even have to try to police anything to get the aesthetics I prefer, that was my point.
But yeah, it's weird the effects of backwards compatibility... so many things decided 40 years ago, which we can't change because it would break someone's configuration.