The 1780 Letter of Eugenius
Eugenius Bulgaris (1716-1806), the Archbishop of Cherson (1775-1779), a man highly credentialed in the Greek language and an ardent advocate of the Johannine Comma, says this in a letter that he wrote in 1780 (the language in bold print is selectively quoted out of context by Frederick Nolan [1784-1864] in footnote 193 on page 257 in his 1815 book, An Inquiry into the Integrity of the Greek Vulgate).
Hoc ego tantummodo in praesenti addere possem, quod a nemine quod sciam hactenus observatum. Tantum scilicet abesse, per interpolationem locum illum surrepsisse, ut ne quidem versus octavus, qui sequitur, staret, nisi versus septimus praecederet, de quo agitur. Quod enim in versione Latina recte exprimitur masculino sermonis genere. Id in ipso textu Graeco originali, non praesupposito superiore versiculo, haud plane consisteret, nisi cum violentia quadam dictionis et per solaecismum patentissimum. Cum etenim, το πνευμα και το υδωρ και το αιμα, nomina neutrius generis sunt, qua ratione concordabit cum iis quod immediate praecedit, τρεις εισιν οι μαρτυρουντες, et quod illico sequitur, και ουτοι οι τρεις, κ. τ. λ.? Maculina equidem nomina et faeminina nominibus adjectivis pronominibusque in neutro genere expressis construi respectu habito ad τα πραγματα id sane linguae nostrae peculiare genium esse omnibus eam callentibus notissimum est. Sed quod etiam reciproce neutra nomina substantiva adjectivis vel pronominibus masculinis aut faemininus indecentur nemo dixerit. Porro hic versu octavo sic legimus, τρεις εισιν οι μαρτυρουντες εν τη γη το πνευμα και το υδωρ και το αιμα και οι τρεις εις εν εισιν. Sed none quaeso dictio naturalis hic et propria potius esset, τρια εισιν τα μαρτυρουντα εν τη γη το πνευμα το υδωρ και το αιμα και τα τρια εις το εν εισιν. At illud tamen est scriptum non hoc. Quae igitur alia ratio occurrentis istius ακαταλληλιας afferri potest nisi sola praecedentis versus septimi expressio quae per hunc immediate sequentum versum octavum symbolice explicatur et plane replicatur allusione facta ad id quod praecesserat? Tres igitur qui in caelo testimonium perhibent, primo positi sunt versu septimo, tρεις εισιν οι μαρτυρουντες εν τω ουρανω ο πατηρ ο λογος και το αγιον πνευμα και ουτοι οι τρεις εν εισιν. Deinceps vero immediate adducti, iidem ipsi testes, quatenus in terra etiam testimonium idem confirment per tria haec symbola versu octavo, και τρεις εισιν οι μαρτυρουντες εν τη γη το πνευμα και το υδωρ και το αιμα και οι τρεις εις εν εισιν. Ac si diceret Evangelista noster, Οι αυτοι εκεινοι οι εν τω ουρανω μαρτυρουντες quod satis indicatur per particulum και cujus vis in praesenti non simpliciter copulativa est, sed plane identifia περι ων εν τω ανωτερω εδαφιω ειρηται δηλαδη ο πατηρ ο λογος και το πνευμα οι αυτοι μαρτυρουντες εισιν και εν τη γη δι ων ημιν συμβολων απεκαλυφθησαν ταυτα δε τα συμβολα εστιν το πνευμα δι ου δηλουται ο πατηρ το αιμα δι ου ο υιος το υδωρ δι ου το πνευμα το αγιον. Και οι τρεις οιτοι οιτινες ανωτερω μεν ανακεκαλυμμενως δι αυτων των υεαρχικων ονοματων εν τω ουρανω μαρτυρουντες παριστανται οι αυτοι εν τη γη δια της εν τη οικονομια μνησεως συμβολικως επανακαμβανομενοι οι τρεις ουτοι εις το εν εισιν. Sed ohe. urceum institui non amphoram.
English translation (the language in [brackets] is added by me for clarification, and the language in bold print is selectively quoted out of context by Nolan in footnote 193 on page 257 in his 1815 book).
This I only in present to insert I would be able, which by no one, as far as I would know, thus far having been observed. So much certainly to be absent through interpolation, that place to sneak, so that not, indeed, verse eight, which follows, would stand, unless verse seven would precede, from which it is derived. For indeed in Latin version it is correctly expressed by masculine of-language gender. This, in original Greek text itself, not having presupposed it to be superior verse, not plainly consistent, unless with some violence of diction and through solecism obvious. Since indeed the spirit and the water and the blood are nouns of neuter gender, by what reasoning would they agree with that which immediately precedes, three they are, the ones bearing witness, and that which immediately follows, and these three ones, and the rest? Truly, masculine and feminine nouns with adjectival nouns and pronouns in neuter gender having been expressed to be arranged with respect having been had to the things [τα πραγματα / the things], that certainly peculiar characteristic of our language to be, with all who being experienced well known it is. But what also reversely, neuter substantival nouns with masculine or feminine adjectives or pronouns they would be indicated, no one has [or would have] said. Again, here we read in verse eight, three they are, the ones bearing witness on the earth, the spirit and the water and the blood, and the three ones for the one thing they are. But not, I ask, natural diction this, and particularly better it would be, three they are, the things bearing witness on the earth, the spirit and the water and the blood, and the three things for the one thing they are? But that nevertheless is written, not this. Therefore, what other reason of that occurring inconsistency [ακαταλληλιας / inconsistency] to be conveyed it is able, unless solely preceding verse seven expression which through this immediately following verse eight is symbolically explained and plainly replicated by allusion having been made to that which precedes? Three, therefore, which in heaven witness They give, first posited They are in verse seven. Three They are, the Ones bearing witness in the heaven, the Father, the Word and the Holy Spirit, and these three Ones one thing They are. Afterward, truly immediately, having been adduced, same themselves Witnesses, where on earth again same witness is confirmed through these three symbols in verse eight. And three They are, the Ones bearing witness on the earth, the spirit and the water and the blood, and the three Ones for the one thing They are. And if he would say, our Evangelist, Those same Ones bearing witness in heaven, as sufficiently indicated through particle και [and, also, even], sense of which in present not simply copulative it is, but plainly identifying, regarding Whom in the above verse it has been stated, namely, the Father, the Word and the Spirit, the same Ones bearing witness, are also on the earth, through which symbols to us They have been revealed. And the symbols are the spirit, though which the Father is indicated, the blood, through which the Son, the water, through which the Holy Spirit. And these three Ones, Who certainly above revealingly through the sovereign names themselves in the heaven bearing witness, are presented, the same Ones, on the earth through the memory in the arrangement, symbolically being taken on again, these three Ones for the one thing They are. But alas, jug [a two gallon vessel] I have instituted, not amphora [a nine gallon vessel].
Eugenius says in his 1780 letter that the added (appositive) nouns πνευμα, υδωρ and αιμα (spirit, water and blood) in 1 John 5:8 in the Received Text express three things (neuter natural gender), and that one would therefore expect the language that is used in association with those three things in that verse to be in the neuter form (τρια … τα μαρτυρουντα … τα τρια / three … the-things bearing-witness … the three-things), but that the masculine form (τρεις … οι μαρτυρουντες … οι τρεις / three … the-ones bearing-witness … the three-ones) is instead used in that verse in reference to the three persons (masculine natural gender) to whom those three things (according to Eugenius) are being symbolically compared in 1 John 5:8 in the Received Text, those three persons being the πατηρ, λογος and πνευμα (the Father, Word and Spirit / three persons) in 1 John 5:7 in the Received Text. Eugenius concludes that the masculine language (in reference to three persons) in 1 John 5:8 in the Received Text is therefore evidence that John wrote 1 John 5:7 in the Received Text (in which three persons are discussed).
However, at the end of his 1780 letter, Eugenius admits that his explanation for the masculine language in 1 John 5:8 in the Received Text is a minor point (a jug / a two gallon vessel) instead of a major point (an amphora / a nine gallon vessel), because his explanation does not actually require John to have written 1 John 5:7 in the Received Text. His explanation is merely one possible explanation for the masculine gender in 1 John 5:8 in the Received Text.
Another possible explanation for the masculine gender in 1 John 5:8 in the Received Text is that the three persons (masculine natural gender) to whom the spirit, water and blood are being compared in that verse are των ανθρωπων (the men) in the την μαρτυριαν των ανθρωπων (the witness of-the men) in verse 5:9. Johann Bengel (1687-1752) subscribes to that explanation on page 145 in the 1873 English translation of the 1759 second edition of his 1742 book, The Gnomon of the New Testament.
A third possible explanation for the masculine gender in 1 John 5:8 in the Received Text is that the Spirit, water and Blood in that verse are a person and two things (masculine natural gender) instead of three things (neuter natural gender), and that the masculine gender in that verse refers the person and two things (the Spirit, water and Blood) in that verse.
According to Bengel and Eugenius (an expert in the Greek language), the masculine language in 1 John 5:8 in the Received Text has nothing to do with the grammatical gender of any noun, and nothing to do with gender attraction, and everything to do with the natural gender (masculine) of the idea being expressed (three persons).
The explanation that the masculine language in 1 John 5:8 in the Received Text (1 John 5:7-8 in the Majority Text and Critical Text) refers to the three persons (masculine natural gender) to whom the Spirit, water and Blood are being compared is the personalization (personification) explanation, which is the traditionally accepted explanation. It is a valid explanation. Even Eugenius (an expert in the Greek language) subscribes it.
Some biographical information regarding Eugenius Bulgaris is found on pages 315-322 in Dialogue 15 in the 1892 book, Neohellenica: An Introduction to Modern Greek in the Form of Dialoque, by Michael Constantinides.