In one of my friend’s tweets, he posted a link to a Slate article that discusses two spaces after periods and how wrong it is. I’ve always been a single spacer so my sensibilities did not get offended so much.
I encountered this convention first during my university days in the Ateneo. Melodie’s MS Word setting would always show the paragraph symbols and she would ensure that after every sentence, there are two spaces. I thought it was just her pet peeve (an OC to an OC), and left it at that. I can’t recall any English or Composition class from my early years in LSGH until my Ateneo days that required me to put two spaces after every sentence. I never thought that it was a norm used by many. It proves that I do not know a lot of things about how the world works.