Sorry for a clickbait title… I wanted one with a play of words.
The article isn’t really aimed at people who are old enough to have learned (learnt for those who speak the English English) typing on typewriters, but also for those who are still taught to use two spaces after every sentence.
The trend has (almost) changed. In the past, people used two spaces for a reason: typewriters had monospace fonts that inserted equal, not proportional, spaces for all letters. So, the “i” consumed as much space as “w” or “m”. The obvious confusion was when sentences ended. So, it was required that the writers insert two spaces after sentences to visibly mark the end of sentences.
Why this post? Now, in 2018? Well, I still come across write-ups from people who use two spaces. I have seen people encourage two spaces, especially in legal documents. I see some people use double spaces in résumés and personal profiles that are not just printed, but shared digitally, as well. In technical publications, we encourage the use of a single space after sentences because we use proportional fonts.
We are increasingly sharing information digitally. Given that context, I’d encourage you to give only space after a period (full stop in the UK English) or any punctuation mark toward the end of a sentence. Not two.