Métaphore - mais réelle. Vécue.*Jean Daive's Récit testifies to his friendship with Paul Celan.
The mais in the laconic pair of sentences (a fragment, fragmentary one-liner) implies that metaphor is usually neither "real" nor "lived", and these incompatibilities (incompossibilities) implied by the quasi oxymoron are indeed among the main reasons for Celan's total rejection of, or objection to, the concept of metaphor; i.e. among the contraindications against its application.
* Jean Daive, La Condition d'infini 5: Sous la coupole. Récit (Paris: P.O.L, 1996), p. 42.