Many French writers and publications will use guillemets when quoting in French, e.g.
Il a dit qu'il « était le meilleur joueur du monde » hier soir.
But there are also major publications such as Le Monde.fr who use (update: used to use) doublequotes; for example, here's a snippet of an article from today:
Les deux portraits étaient légendés par ces mots : “Choc de titans”.
So, how commonly are double quotes used in French writing, when quoting? Is it only in certain publications like Le Monde.fr that they are used, or is it more commonplace? Are guillemets ever used outside of France?
Additional query: In English, single-quotes are also a valid replacement for doublequotes (they are more typically used in British English), and so the following two phrases are the same:
He said, “I want it soon” to me.
He said, ‘I want it soon’ to me.
Can single-quotes be used in French in the same way that doublequotes are?