@marinelife, I don’t see what correction you are making with “Actually.” It seems to me that the article says just what I said: that typesetters wanted to see two spaces in manually typewritten manuscripts from which they were setting type for printing. Quoting: “Monospaced type gives you text that looks ‘loose’ and uneven; there’s a lot of white space between characters and words, so it’s more difficult to spot the spaces between sentences immediately. Hence the adoption of the two-space ruleāon a typewriter, an extra space after a sentence makes text easier to read.” Typesetters wanted original manuscripts to be easier for them to read so they could set them correctly.
This didn’t mean that they were going to set it that way, only that they wanted that extra visual aid in the source document. Only the typesetter (and editors and other production people) was going to see that.
In fact, I believe that magazine editors also used to require two spaces in manuscripts submitted for consideration, and (again if I recall correctly) failing to do so was enough to get your ms. pitched into the reject pile. Not now, of course, since electronic documents have completely changed the nature of submissions.
If no distinction is being made between book typography and what an author hands in, and these days there may not be any, that doesn’t change the fact that it came about when those were two separate operations. And so typing teachers taught all students to follow the two-space convention, presumably because one or two of them somewhere were going to be handing a manuscript in for publication.
I never thought that a typewriter’s monospacing was considered a design flaw; rather, it was just a limitation of the technology available to that point. Isn’t that so?