Commentary Par XI 73

Thomas is concerned lest he had allowed his speech to become chiuso (dark, unclear) and we consequently not understand of whom and of what he spoke, thus reflecting his characterization ([Par XI 22-24]) of his figurative speech in the previous canto (most specifically at [Par X 96], his metaphor of fattening sheep, on which he has been expanding here) as not being aperta (clear).  Once again one may witness, behind the text, Dante's desire to deal with Thomas's attacks on the unreliable nature of poetic speech (see Hollander [Holl.1976.1]).