Jeffrey Schwab wrote:
> The Handbook itself uses only single spaces at the ends of sentences.
> Still, I hardly think there is one conclusively "right" or "wrong"
> convention.  Until I am convinced otherwise, I will continue to use two
> spaces to separate sentences.  This makes sentences easier to lex with
> regular expressions, and makes them stand out to text editors and human
> readers.

 "Right" or "wrong" in this kind of styling has to do with whether
something is right or wrong according to a particular convention.

The normal convention for professional typography is to use one space
between sentences, whether you are convinced or not, whether using hard
type, a professinoal typesetting program, a desktop publishing program,
or a word processing program.

The older typewiter conventions are still often requested for
manuscripts for academic essays and mansucripts for submission to
publishing houses. These conventions also require underlining rather
than italics, use of double-hyphen for a dash rather than the specific
dash character, and so forth. But should this same manuscript be
professionally printed, even if the text is actually to be set by a
word processor, it would almost certainly be edited first to convert it
to typographical standard: changing all double-spaces to single spaces,
all occurrences of double-hyphen to em-dash or en-dash, using fancy
quotation marks instead of possible straight typewriter quotation
marks, italics instead of underlining, and so forth.

Note that HTML has from the beginning automatically changed any
multiple runs of spaces into a single space when displaying text.

Yes, a convention of always using two spaces would make sentences
easier to lex with regular expressions. Similarly, enforcing one single
spelling of English throughout the world would make searches and
matches easier. However, it is philosphically unsound to ask that the
world change to fit particular data-processing routines, rather than
that data-processing routines be built to properly to deal with
real-world situations.

If your lexing routine fails because many people don't end
non-paragraph-final setences with double-spaces, or do so only in
particular plain text files, it is the fault of your lexing routine for
failing to handling common formatting, unless your lexing is intended
to be a limited tool that works only with manuscript formatted text.

The best general sentence lexing algorithm I've seen is the one set
forth by the Unicode Consoritium at
http://www.unicode.org/reports/tr29/tr29-4.html#Sentence_Boundaries .
This is designed to work reasonably well in any language and writing
system supported by Unicode, not just in English.

Jallan