I'd be surprised if the Jewish Christian communities in Israel/Palestine didn't keep kosher. I've known a few non-observant Jews in the U.S. who keep kosher (albeit not the strict standards that halakha requires).
It's a bit strange, innit, that quite a few Jewish people who are atheists still maintain dietary laws and other rules (even Shimon Peres, who says that he's not religious, made quite a scene when he refused to travel on Saturdays and thus could not make it to the Olympic ceremonies last summer from his hotel), but here in America we can't even get many Orthodox Christians to fast at all, even half-assedly (I'll admit that I am terrible with fasting m'self)
Anyway, has anyone here ever been to Israel and met people from the Israeli community? I have a love of all Jewish languages, so I was bored one day and Googled "Yiddish translation of Saint John Chrysostom" (I really have no life; maybe my friends are right in that I should go clubbing with them
). While I haven't found Yiddish (yet!), I have found Hebrew, and the story of how refugees from the Soviet Union who were sometimes only 1/16th or 1/8th Jewish claimed the Right of Return and settled in Israel. Some have retained the Russian language, others have embraced Hebrew. This is all I could find on the liturgy in Hebrew: http://www.youtube.com/watch?v=WGSM9oRr1Mo&lc=GfjJdS06bt4kAxZ6IjeR_m4EI0I0Z12ggr3TCQ91lcg
Also, I was surprised to find out that there are more Jewish Christians in Russia than I ever thought (not that I ever thought that there were many, or that I ever really thought about it at all). The best example I can think of is that a speaker in the Knesset, Yuli Edelstein, is the son of a priest, Georgy Edelstein, who serves in Karabanovo. Does anyone know of any more interesting stories about Jewish Orthodox-Christians?