It's an old topic, but Ormsby is smart enough to make it interesting again.
It's one thing to learn a foreign language well, quite another to learn it well enough to be able to feel in it, and harder still, if not impossible, to master an alien idiom so completely as to convey the force of what you feel. A few modern writers have made the leap: Joseph Conrad and Vladimir Nabokov in English, Samuel Beckett in French. But all three wrote their best work in prose. I can't think of a single poet, who has written great, or even noteworthy, poetry in a language other than his or her own. Poetry, it seems, can only be written well in one's mother tongue. This was the opinion of W.B. Yeats who dismissed Rabindranath Tagore's English verse, even though it won the Bengali poet a Nobel Prize. In our own day, one has only to read a few poems by the late Joseph Brodsky to realize that his English verse is, for the most part, hopelessly inept. Brodsky struggles constantly to escape the confinement of his adopted idiom but his English falters, always in small but fatal ways, in the process. (You can read the rest at The New York Sun)