I think he was saying that when you speak about "Torah observance" then you are referring to what Judaism recognizes as Torah observance. Otherwise, it would sound better to say "OT observant" or some such. Usually, Jews are the ones to refer to Scriptures as "Torah" so it can come across as offensive as when some Christians call themselves "Messianic Jews".
It's not the same thing at all though. So-called "Messianic Judaism" came out of Christianity, not Judaism. And Messianics are generally not Torah observant except culturally speaking or as a way to connect Jewish ritual to Christian concepts. What I am talking about is a group of Torah observant Jews who came to believe in Jesus as the Messiah. They retained their Jewish identity and did not see themselves as following another religion. They continued to attend the synagogue, to make pilgrimage to Jerusalem for the festivals, to observe the Sabbath and keep kosher, and circumcise their male children.
In matters of law they deferred to the rulings of the Pharisees (
Mat 23:2-3) but they did reject some of the oral tradition. But their different interpretation of the Torah as expounded by Jesus in chapters 5-7 of the Gospel of Matthew did not really change their fundamental observance. They simply eschewed the taking of oaths, refrained from divorce for reasons other than infidelity, refused to avail themselves of legal remedies when wronged, and avoided ostentatious displays of religiosity.
Because of their insistence on the need to observe Torah they were eventually declared heretics by the Roman Catholic Church in the fourth century. Epiphanius the heresy hunter wrote of them in his
Panarion as follows:
7,1 But these sectarians whom I am now sketching disregarded the
name of Jesus, and did not call themselves Jessaeans, keep the name of
Jews, or term themselves Christians-but "Nazoraeans,'' from the
place-name, "Nazareth," if you please! However they are simply com-
plete Jews.
7,2 They use not only the New Testament but the Old Testament as
well, as the Jews do. For unlike the previous sectarians, they do not
repudiate the legislation, the prophets, and the books Jews call
''Writings.'' They have no different ideas, but confess everything exactly
as the Law proclaims it and in the Jewish fashion-except for their belief
in Christ, if you please! For they acknowledge both the resurrection
of the dead and the divine creation of all things , and declare that God
is one, and that his Son is Jesus Christ.
7,4 They are trained to a nicety in Hebrew. For among them the en-
tire Law, the prophets, and the so-called Writings-I mean the poetic
books, Kings, Chronicles, Esther and all the rest-are read in Hebrew,
as they surely are by Jews. They are different from Jews, and dif-
ferent from Christians, only in the following. They disagree with Jews
because they have come to faith in Christ; but since they are still
fettered by the Law-circumcision, the Sabbath, and the rest -they are not in
accord with Christians. As to Christ, I cannot say whether they too
are captives of the wickedness of Cerinthus and Merinthus, and regard
him as a mere man-or whether, as the truth is, they affirm his birth of
Mary by the Holy Spirit.
Panarion 29- The Nazarenes - Nazarene Space
That's actually a great example. It's not rare to not count Meshichists for a quorum for prayers. I live in an ultra-Orthodox town that has a large Meshichist community and theirs a certain amount of disconnect between the rest of us and them. In fact, the term Meshichist was purposely given them because it sounds like "MaSHCHiS" which means "destroyer".
So today as in yesteryear, these sub-sects tend to branch off and disconnect.
Yes and that may happen with the Meshichists in the same way it happened with the Christians. They may end up as a separate religion.
Does something that develops among Orthodox Jews make it an Orthodox practice even if it is at odd with Orthodoxy? Meaning, if a group of Orthodox women would start taking multiple husbands, would that make it an "Orthodox" or even "Jewish" practice or would you define that as a splinter-sect?
I think it is a splinter sect and obviously is at odds with Orthodoxy. I'm just pointing out it can develop within an otherwise Orthodox community. But we have to keep in mind that in the first century there was no "orthodoxy". There were different sects of Judaism at odds with one another. The Nazoreans were simply another one of those sects. Looking back in hindsight from the later Jewish perspective one can see those other groups as heretical but that was not the case during that time period. Each disparate group saw itself as representing normative Judaism.