Best reference I could find is here: https://www.lalanguefrancaise.com/articles/espace-insecable https://www.lalanguefrancaise.com/articles/espace-insecable Ac

Best reference I could find is here: https://www.lalanguefrancaise.com/articles/espace-insecable https://www.lalanguefrancaise.com/articles/espace-insecable Actually before the ":" specifically there should be a regular non-breaking space, not a narrow one. Except in Switzerland. Other punctuation marks take the narrow non-breaking space.