Don’t go down the “add or subtract” argument. It is full of holes. That statement in revelation refers to THE Book Of Revelation. The bible is a collection of BOOKS.
I think that one of the main reasons for the non-acceptance of the Mormon baptism is the fact that you have to accept Joseph Smith and declare that the Mormon church is the one true church. In that statement Mormons extract themselves from the body of the christian church which does not reside in a building.
Well even in the book of Revelation, I believe Joseph Smith added 59 words with his JST version.
(I've got the exact # & which words were added...can revisit this later...I think Elsie also has this info)
Just to correct you, the warning to not “add” or “subtract” although it speaks directly about the very last book of the Holy Bible, also does extend to the NEED to show RESPECT to God’s Holy Bible, His holy word.
That is why the Bible is also called a LIBRARY.
The CHURCH is MORE than a building. It is the “body of Christ”.
Also it is possible that because of a pratice of what is called “baptism of the dead”, which, did not Paul warn against in one of his letters not to do?