Just what I don't need, another Wikipedia edit-war. My attempt to clarify a subtle point in Sentence_spacing yesterday has been undone (by Cybercobra), so I've tried a 2nd time to eliminate some misguided speculation based on a misconception. This is reminiscent of a similar point in the ASCII article I've had a war over, where some jerk and his sock-puppet are badly in need of more slandering than I've done until now, and I hope she reads this.
Darn, my 2nd attempt has been reverted too (by Nuujinn). Does every Wikipedia contributor except me have a sock-puppet I wonder? I thought it was only the fascist ones:-) It must be time to explain the problem on the Talk-page... I've twice attempted to make my point in the article, but it gets undone. Looking at the Discussion page for the article shows there's already been extensive debate over that "is obsolete" wording, and I'll just bow out quietly.
The argument made in that article that proportional fonts have made double sentence spacing obsolete because these fonts can assign a wider spacing for terminal punctuation characters than for other punctuation characters is fatally flawed because it assumes a character-code for Period distinct from Dot which is not the case.
Incidentally I was taught to use 2 spaces after a sentence, and I still like things spaced that way. However it is true that most major style-guides these days want just one space after a sentence.
I've observed that there's more to my spacing preferences than merely wanting 2 spaces after a sentence. I find myself using an extra space in many circumstances, such as after a semicolon, after a colon, sometimes even after a comma.
It comes down to matters of taste. Taste in font-design. There's been a widespread love-affair with "Condensed" fonts, and that's what I'm reacting to. One of the side-effects of this love of condensed fonts is the miserly amount of horizontal space that's typically alloted to inter-word and other spaces. Along with my preference for an "Expanded" font comes a craving for slightly more generous horizontal spacing in general. Which has a lot to do with my thinking that text looks better when an extra-wide inter-sentence space is employed.
Incidentally, the miserly horizontal spacing has come about largely by accident. Type designers were designing for printing applications where type would be "justified", meaning the spaces would be made wider to make each "line" exactly fill the column. Thus they chose a spacing that was not the "ideal" but rather the bare minimum of what was considered acceptable, and in real life the spacing would almost always be somewhat more generous. These days we mostly do not "justify" and by accident that has given us not what the font-designer thought of as "ideal" but rather what was thought to be the barest minimum of acceptable. Whenever we employ "unjustified" text we really ought to scale up the spaces by something like 30% to get us into the "sweet" part of the range that the spacing was designed for.
Most people (IMHO) use a fontsize that's far too big (Microsoft defaults likely the main reason), and then choose a condensed font. Methinks it better to choose a much smaller size, and then to pick a font that's the opposite of condensed. In other words a font that remains legible at small sizes.
[This was an entry in my "blog about everything"; upon adding the explanation that matters of taste are involved it merited being its own rant]