Tiens je tombe sur cette discussion sur un forum :

Anyone know why ' changed in fonts to not lean? I remember 'quoting' used to be wrapped in right-leaning apostrophes on both sides at one time on ASCII terminals.

Well, this changed with the 1986 revision of ANSI X3.4, and I expect Latin 1, Unicode, etc. share the new definition of '. The code point used by Latin 1 for the acute accent was apparently unused in DEC MCS. Why ANSI had to change it, I don't know, but there's no going back.

(Pour info, Nil, la discussion pose sur les problèmes de rétrocompatibilité que pose ce changement . Dans groff en l'occurrence : http://www.mail-archive.com/groff@gnu.org/msg04165.html . Et tu voudrais me faire gober que l'apostrophe est droite... pour raisons de rétrocompatibilité )