I love Tyutchev -- you're really in for a treat!

Archipoeta springs to mind, but of course besides his poems nothing remains of his work, as far as I know.

Mirsky's book (in Italian we transliterate it Mirskij) used to be my favourite, too. He wasn't really a good literary critic (at least, not in my opinion), but he made every author sound so interesting...

Not so curious if you consider the history of Hebrew literature. Before the emergence of native Hebrew speakers at the first half of the last century all the important Hebrew writers were more comfortable speaking in Yiddish, Russian and Polish rather than in Hebrew.

Good point.

And ... I assume that there's an element of hyperbole (or thinking in Russian and writing in English) here as well.

He may not have used Russian as a home language but "In private and public life he spoke and wrote nothing but French" strikes me as incredibly unlikely.

I've noticed that in Polish, words usually translated as 'always' and 'every' often mean something more like 'usually' or 'most' and I wouldn't be surprised to find the same pattern in Russian as well.

What Kobi said doubly applies to Jewish authors who normally spoke and wrote (Judeo-)Arabic, but wrote (secular) poetry exclusively in Hebrew. Obviously this wasn't for lack of familiarity with Arabic language and literature, quite the contrary: some of the most prolific and best Hebrew poets came from Muslim Spain, like Yehudah ha-Levi who wrote poetry in Hebrew, but Kuzari is written in Judeo-Arabic. This curious duality remains one of the great unanswered questions of Judeo-Arabic studies. Some authors, like Rina Drory, argue that this was because of a kind of functional diglossia in Jewish community: Arabic served the communicative function while Hebrew as the holy tongue was more fit for the literary and esthetic purposes. Others, like Joshua Blau, disagree and point out that Jewish poets did indeed write poetry in Arabic, but such poetry was directed at Muslim audience and was not a part of Jewish culture, but rather of Muslim culture.
The question here is whether such poems were written not only in Arabic style, but also in the Arabic script. If so, one could point out that such the language of those poems is Muslim Arabic and not Judeo-Arabic and the statement "There is no secular poetry in Judeo-Arabic" would still hold true. Somebody should look into it...