I imagine a thread like this, a “Protestant/Orthodox caucus” thread could be used as much to discuss things that are different between the two groups as are in common.
In other words, as long as the discussion was kept to the particular beliefs of the two groups, it would be possible to discuss the differences that lie between them. The Orthodox, as an example, could provide their view of icons, and the Protestants thereby oppose those views with their own.
The Protestants could defend the solas, and the Orthodox could attack that defense.
But I guess my difficulty is, if the caucus label is going to be used to “screen out” certain folks, i.e., Catholics, then what happens if topics discussed include things believed by both Orthodox AND Catholics? After all, Catholics accept icons, and fully agree with Orthodox explication of the theology of icons.
To attack the theology of icons is to attack Catholic belief as well as Orthodox belief. How could a caucus thread that excluded Catholics be used to discuss the theology of icons in a negative way? Would not Catholics have a right to offer defense for this shared Orthodox/Catholic belief?
Thus, trying to restrict the caucus to topics of either only Protestant or Orthodox interest might yield a rather number of limited topics that one might discuss about Orthodoxy, and, ironically, perhaps all of those topics might be inappropriate for a caucus thread, in that those topics would almost certainly be points of contention between Orthodox and Catholics.
It seems to me that the only fit subject matter for such a caucus would be uniquely Protestant beliefs - the Protestant defense thereof and the Orthodox argument against them. And, of course, if the Protestants desired a caucus designation, their arguments on behalf of their uniquely Protestant beliefs would have to be presented in a way that didn't disparage those beliefs of the Orthodox held in common by Catholics, and also didn't disparage the beliefs of Catholics NOT held in common with the Orthodox.
Perhaps this particular caucus combination is a chimera.
sitetest
If a Protestant thinks that Protestants and Orthodox are in substantial agreement in other major areas they need to address these:
1. The Real Presence in the Eucharist.
2. The Theotokos and the Dormition.
3. Rejection of sola scriptura.
4. Iconography.
5. The Deuterocanonical Books.
For instance, a Catholic Caucus may discuss the "Our Father" prayer without threat of disruption by non-Catholics who also pray the same words.
In a "Protestant/Orthodox Caucus" - the members are free to discuss both the beliefs they share and the ones they don't, provided they do not speak against/to the beliefs of non-members because once they do, the non-members have an interest in speaking for themselves.
The underlying principle is that the caucus must not be used as cover to attack the beliefs of non-members.
The caucus may have discussed the five Solas, icons, Christ, etc. But once they say "Catholics believe" or "we disagree with the Catholic doctrine of" or the "LDS teaches" etc - then the caucus is broken.
The article of this thread would have been appropriate for a Protestant/Orthodox Caucus were it not for Chapter 10 which is a thinly veiled reference to Papal Primacy, a belief of Catholic non-members.
The moderators are responsible for making judgment calls. This one is on me. I found the reference apparent even though it did not specifically say "Papal Primacy."
On other caucus threads which were in dispute, I have made similar judgment calls, e.g. whether a statement made concerning non-members was merely history or whether it was an attack against or representation of what the non-members believe in contrast to what the members believe.