"The Oneness Pentecostals stress that God is absolutely one (Isa 44:6, 8, 24)—that is, one without distinction of persons. There are no distinctions in God’s eternal being, and the Godhead does not consist of three centers of consciousness (as some Trinitarians hold). Moreover, in Jesus dwells all the fullness of the Godhead bodily (Col 2:9)." (Oneness Pentecostal Confession. 9,34. 2007)
If you are KJV Only you don't want to read any further. Text critic, Daniel Wallace finds the Comma Johanneum in the margins of an eleventh century parchment manuscript at the BSB. The margin notes, containing the reference, are very similar to what may have been "made to order" for Erasmus in 1520.
Wallace says, "The original wording of 1 John 5.7–8 in the manuscript at the BSB reads, For there are three that testify, the Spirit, and the water, and the blood; and the three are in agreement. This is unremarkable as it is, since this is the wording of the original text of this passage. But there is a note written above the text in the upper margin which reads, There are three who testify in heaven: The Father, Word, and the Holy Spirit, and these three are one. The note is written in a much later hand—at the earliest during the second half of the sixteenth century."
Wallace wisely does not feel the Trinity rises or falls on the Comma; however, is this not an obvious Trinitarian bias emerging in the translation process?
I for one am glad this discovery was found and pray that translators strive for excellence in translation, careful not to impose Trinitarian notions where they are not "explicitly" referenced, in the Text itself. I believe the references of distinction must center upon the Incarnation as we protect the divinely revealed first principle of absolute monotheism as well as His eternal essence.
Personally, I find that there is evident bias by the Trinitarian translators (c.f. Rev 5:6). I am no expert in the field of textural criticism nor the original languages but it is fairly easy to deduce certain conclusions on the evolution and development of the Trinitarian doctrine.
In addition, and to some "more importantly", this margin note on the Comma (1 John 5:8) is often used to support KJV Onlyism since they are committed, whether they realize it or not, to the Textus Receptus. Many feel that the Comma was an interpolation, something added to the copy or manuscript by a "later hand". It eventually made its way into common translation, see KJV 1611/Erasmus/Froy, etc.
Although some have retained it many modern translations omit the Comma and place it into the margin or footnotes. Personally, I do not feel the Comma Johanneum is a part of the originally inspired writings of Scripture. This should not cause us to fear or abandon but to draw us closer to God's Word and create an hunger to KNOW more about what He has said.
The problem is that we are English speaking folk attempting to read a document dually authored by God and written by about 40 Jewish men and probably one Gentile (Luke). It is inspired or "theopnuestos" - breathed out by God but in the process of moving the letters of those documents to another language it makes bias possible. Interpretation is inherently present. I think the bias is actual in reference to the Comma.