What language should poets write in?

She [Marina Tsvetayeva] herself passionately believed that "writing poetry is in itself translating, from the mother tongue into another, whether French or German should make no difference."

No language is the mother tongue. Writing poetry is rewriting it…. A poet may write in French; he cannot be a French poet. That's ludicrous…. The reason one becomes a poet…is to avoid being French, Russian, etc., in order to be everything…. Yet every language has something that belongs to it alone, that is it…. French: clock without resonance; German—more resonance than clock…. French is there. German becomes, French is.

-Tsvetayeva chiding Rilke as qouted by John Bayley in "Big Three"
New York Review of Books Volume 32, Number 19 · December 5, 1985

According to Sartre...

"Many young people today do not concern themselves with style and think that what one says should be said simply and that is all. For me, style—which does not exclude simplicity, quite the opposite—is above all a way of saying three or four things in one. There is the simple sentence, with its immediate meaning, and then at the same time, below this immediate meaning, other meanings are organized. If one is not capable of giving language this plurality of meaning, then it is not worth the trouble to write.

What distinguishes literature from scientific communication, for example, is that it is not unambiguous; the artist of language arranges words in such a way that, depending on how he emphasizes or gives weight to them, they will have one meaning, and another, and yet another, each time at different levels."

-Sartre speaking to Michel Contat

New York review of Books, Volume 22, Number 13 · August 7, 1975