I am not sure about the exact details, but there is a famous group of
Russian nationals, who did *not* officially convert, (through a beit din) but
started to live like Jews. They were called "Sobotniks", because they kept
the Shabbat. They did live in specific communities. I am not sure whether
the Jewish community accepted them as Jews. Some were among the early
settlers of the Land of Isreal.
Maybe this is what the writer of the original message is referring to.
Johannesburg, South Africa