@davidfor : yes , i was agreeing with you (and was too tired to be clear haha) ; in french the correct use for a fixed width would be the narrow non breaking space but whatever. (there is a distinction in french between a non breaking space with fixed width and a "variable width" non breaking space). this distinction is irrelevant in english because there is no need of a space before punctuation.
@Semwize : as i linked above: because of a bug so old it became a fact
(but I'm still saying in case of dialogues, the stretching is ulgy and problematic for the reading so I use epubs
(it's the only case where it's a real problem, in fact) In french dialogues must be aligned (each first word after each dash have to be aligned, as a rule)