“What about whether “signs” are still valid?”
A valid point. Some churches go to either extreme, either requiring signs or refusing to acknowledge any. It is certainly an area that divides churches.
FWIW, my sister is a Trinity-believing pentacostal and I am not, but we’ve both worshiped without a problem in each other’s churches. But you are still fully correct to add that to the list I gave.
There are probably others, but I doubt a very good list would run beyond single digits. American and Southern Baptists, for example, split in the 1800s over the issue of missionaries owning slaves. I’m a Southern Baptist since I’m a member of an SBC congregation, but I was baptized by an American Baptist. I’ve known baptists who were baptized by Lutherans and Methodists. For membership, our congregation requires believer’s baptism, but we do not specify any denomination.
To be honest, belief in the Trinity is one of the best ways of discerning between cult and Christian. We would accept baptism by a Catholic priest, provided it was done as recognition of conversion and not an an infant. We would not accept it from the LDS, or a pentacostal church that rejected the Trinity.
I agree that a shared doctrine on the Trinity is one of the best ways to discern between Christians and Cults. We Catholics consider Baptisms by other sects valid. We stopped accepting baptisms done by LDS a few years ago when it was made clear that their understanding of the Trinity was far different from traditional Christian belief.
May the Joy of awaiting the celebration of Christ’s Birth enlighten your heart and home.