From the “Yet Another Subject For A Holy War” Department, Microsoft is
planning for the next update to Word to flag two spaces after a full
stop and before the next sentence as a typo
Two spaces after a full stop was long-standing practice for typewritten
text, and carried over to some extent to computer users. But with the
advent of WYSIWYG word processing and proportional fonts, it became
more common to adopt the practice of typeset text, and only put one
space after a full stop, before the next sentence.
Where do you stand? Microsoft ran a poll on the question, and it seems
the majority favoured a single space.