We debated this in 1993 on the www-talk mailing list [1]. Terry Allen (an editor at O'Reilly) wanted rendered HTML documents to follow Tex conventions with extra space after a period. Marc Andreessen (still at NCSA in 1993) pointed out browser developers couldn’t do the syntactic analysis required to distinguish the end of sentences from inter-sentence periods. Guido van Rossum (working on Python version 1.0 at the time) weighed in on the whitespace issue and complained “it’s mostly propaganda by Knuth and Kernighan (TeX and troff) that makes people want this.” We ended up with browsers collapsing spaces between sentences for the web. Most style guides [2] seem to have settled the issue in favor of a single space but debate rages, eh?
[1] http://1997.webhistory.org/www.lists/www-talk.1993q3/index.h...
[2] https://en.wikipedia.org/wiki/Sentence_spacing_in_language_a...