"...English, Russian, and French, who have done it at least as well as I have. Funny, I notice that when mentioning my three tongues, I list them in that order because it is the best rhythmic arrangement: either dactylic, with one syllable skipped, "English, Russian, and French," or anapestic, "English, Russian, and French." Little lesson in prosody."

And minds that died before arriving there:

Poor old man Swift, poor —, poor Baudelaire

CK: "...the name required here must scan as a trochee. Among the names of celebrated poets, painters, philosophers, etc., known to have become insane or to have sunk into senile imbecility, we find many suitable ones."

C.Kunin: the first line of Pushkin's poem on his fear of losing his mind. Ne dai mne bog soiti suma. Stresses fall on dai, bog, -ti and -ma. My guess to Jansy's question would be
Poor Swift, poor Kinbote, poor Baudelaire.The stresses would fall on Swift, Kin- and poor... With a secondary stress on -laire.

Jansy Mello: Hardly Kinbote! At most, poor Shade. Although the BBC-2 Interview is distinct from CK's commentaries, I'm inclined to think that the missing name must belong to some Russian artist, Dostoevsky (too long), Gogol..(The first in Shade's variant is a British satirist's, then enters the dash, then a French poet. An attempt at self-parody (the poet who rose as a comet and disappeared) might lead us to Sirine.