Isn't it the so-called "default role" of Sphynx > 0.4 http://sphinx-doc.org/config.html#confval-default_role ?

@NelleV : is it a "can" or a "should" ?
I understand from MEP10 that all cross-references will have at some point to be updated "in a semi-automated way" with this format (provided this default role doesn't get ambiguous, though).
Note that I would be happy to do it if it is the recommandation, I am just asking.