Borges says that
a] a translation, logically, can be superior to the original in verbal terms. The example he give is
"when all my house was hushed" as a translation of "estando ya mi casa sosegada" [Roy Campbell translating SJ of the Cross]. JLB says that this line is better than the original.
Another example is "the lyf so short, the craft so long to lerne" which is certainly more poignant than the Latin tag "ars longa, vita brevis" the Chaucer was translating in this line of his poetry.
In many cases, if not almost always, the translation is not superior.
But the superiority of the original is not verbal, in essence, but a function of the value we place on its being the original. This is the second part of this idea that is even more brilliant, and which I missed the first dozen times I reflected on the first part of the idea.
So a translation can be as good as it wants to be. There is no limit, and it can surpass the original, but it will never have that ontological status.