> (Yes, the double space after the period is a built in habit from typing class, and a debatable item in the computer age, but nobody seems to care one way or the other.)
Well, it does serve a purpose in the computer age - grepping for sentence ending.
Also, it makes it easier to determine when a sentence ends that contains an abbreviation. (This refers to when most people would use periods at the end of abbreviations.) I still use double spacing even though standard HTML does not display the double spacing on web pages.
The following sentences are an example of what I was saying:
"I sent the N.D.A. to N.Y. It arrived three days later."
The single space after the "A" in "N.D.A." indicates that the sentence has not ended even though there is a period.
The harder case is an [A-Z]. [A-Z] which is not a sentence ending. Consider the following:
"When we compare the use of mistakes in speech in the Saga of St. Olaf with some of the other Old Norse literature, we can see that there is, in fact, a pattern of use of errors in speech being a sort of death omen."
The single space there identifies that there is no end of sentence between St. and Olaf. Of course when you are working in LaTeX you have to tell LaTeX that this is a word break and not a sentence break or else it will kern it as an end-of-sentence.
Well, it does serve a purpose in the computer age - grepping for sentence ending.