FD is old enough to have learned to type on an Hermes manual typewriter. FD did not really learn to type in the high school class where the typewriters were even older. However, the idea that one should put two spaces after the period of a sentence was probably learned in class. And, despite changes since then (well described by Farhad Manjoo in his recent Slate essay “Space Invaders: Why you should never, ever use two spaces after a period”) FD is still using two spaces after a period.
Manjoo says typographers don’t like the two-space idea, and say it is not esthetically pleasing. It’s an artifact, they/he say/s, based on the way in which old fashioned manual typewriters functioned. In an age of variable type fonts, no extra space is needed. But FD finds another reason for using two spaces to indicate the end of a sentence. If one uses one space to show the end of a word, why not use two spaces to show the end of a sentence, which is a larger unit of thought.
But it seems to FD that the whole question is one of habit or custom. The ways in which written words are displayed has changed a lot over time. Many Ancient texts have no space between the words, which must have made reading challenging and perhaps could lead to some interesting misreadings. Using a “capital letter” at the beginning of a sentence isn’t so old, either — and some languages do not even have different two different forms of each letter, as we do in English.
So, despite Manjoo’s distress, FD will be keeping the FD Blog full of “extra” space.