Edward F. Hills speaks of the grammatical issues the omission of the comma causes:
“… the omission of the Johannine Comma involves a grammatical difficulty. The words spirit, water, and blood are neuter in gender, but in 1 John 5:8 they are treated as masculine. If the Johannine Comma is rejected, it is hard to explain this irregularity. It is usually said that in 1 John 5.8 the spirit, the water, and the blood are personalized and that this is the reason for the adoption of the masculine gender. But it is hard to see how such personalization would involve the change from the neuter to the masculine. For in verse 6 the word Spirit plainly refers to the Holy Spirit, the Third Person of the Trinity. Surely in this verse the word Spirit is “personalized,” and yet the neuter gender is used. Therefore, since personalization did not bring about a change of gender in verse 6, it cannot fairly be pleaded as the reason for such a change in verse 8. If, however, the Johannine Comma is retained, a reason for placing the neuter nouns spirit, water, and blood in the masculine gender becomes readily apparent. It was due to the influence of the nouns Father and Word, which are masculine. Thus the hypothesis that the Johannine Comma is an interpolation is full of difficulties.
