Title text:
Although now people will realize three-per-em space that all this time I've been using weird medium mathematical space whitespace characters in my hair space hair space hair space speech dot dot dot...
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3143/
I've heard some people use it when they don't have the rising inflection in their voice that usually denotes a question. I've also used and seen it used to mean dubious claim as the other poster mentioned! Not very commonly though.