Commentary Purg XXVI 117-118

What does it mean to say that Arnaut was 'a better craftsman of the mother tongue'?  Not, it would appear, that he wrote poems that were better in substance than those of others, but better in style, better made.  It is possible that Guinizzelli's language reflects the claim that lay latent (but clear enough) in some poems of Cavalcanti, who liked to use the image of the file (limo), an instrument used to refine one's handiwork, to suggest the careful nature of his own poeticizing.  Dante here would seem to be, through the testimony of Guinizzelli, taking some of that distinction away from the other Guido and, in a sense, replacing him with Arnaut, a craftsman not only better than he, but better than Cavalcanti, too.

      The 'mother tongue' here not only refers to Arnaut's langue d'oc, his native Provençal, but to any Latin-derived vernacular (see Sordello's similar remark, addressed to Virgil, at [Purg VII 16-17], which also makes Provençal the child of Latin: 'O glory of the Latins... through whom our language showed what it could do').

      Guido also seems to mean that Arnaut's vernacular verse was stylistically better than anyone else's writing in the vernacular, whether in verse (in the langue d'oc -- Dante is cavalierly unconcerned, at least publicly, with French poetry) or in prose fiction (in the langue d'oïl, since according to V.E.I.x.2 all vernacular prose was written in French).  This passage is the cause of much debate, one issue in which centers on the question of whether or not Dante means that Arnaut himself wrote prose fiction.  This seems more than dubious.  See Poletto's comment to this effect (DDP Poletto.Purg.XXVI.118-120).