While on the subject of typography, here is an absolute rule, not subject to serious debate: Unless you’re banging out your briefs on an Underwood manual typewriter, put only one space—not two—between the end of one sentence and the first letter of the next sentence. On this point, the authorities are unanimous:
“Use even forward-spacing in your documents: one space between words and one space after punctuation marks (including colons and periods).” Bryan A. Garner, The Redbook § 4.12 (2013).
“Some topics in this book will offer you choices. Not this one. Always put exactly one space between sentences.” Matthew Butterick, Typography for Lawyers 41 (2010) (emphasis in original).
“A single character space, not two spaces, should be left after periods at the ends of sentences (both in manuscript and in final, published form) and after colons.” The Chicago Manual of Style § 2.12 (15th ed. 2003).
“Space between sentences. In typeset matter, one space, not two (in other words, a regular space), follows any mark of punctuation that ends a sentence, whether a period, a colon, a question mark, an exclamation point, or closing quotation marks.” Id., § 6.11.