An objection notes that the restriction “convention of discourse” is explicit in the definition of metaphor but not always repeated in exactly the same wording in the definition of literal use. This may make the definitions appear asymmetrical.
The reply asks whether the term assignment (waḍʿ) already presupposes the recognized assignment within the relevant speech community or technical domain. Where that is implied, repetition of the phrase need not add a new condition.
For practical classification the convention still must be identified. Otherwise participants may be judging the same utterance against two different established vocabularies.