This post is a good start:
Pure Bible Forum - 2014
Heavenly Witnesses and the Grammatical Gender
Next there is a reference to Gregory Nazianzen for which Bill Brown uses the James Snapp post here, as if this is some great revelation that I missed:
===[TC-Alternate-list] First John 5:7 and Grammar
James Snapp - 1/16/2008
... It looks to me like the true object of Gregory's protest is not the grammar of the verse, but an over-strict application of grammatical rules upon it. John was not consistent in the way he has happened upon his terms, as Gregory put it, but if Gregory had felt obligated to defend the grammar of the passage, rather than delineate his opponents' views of it, I think he would have argued that considering the special nature of the witnesses, John's choice of words is grammatically acceptable.
And clearly, by this reasoning, there were others who thought that John's choice of words (in the abbreviated text) was NOT grammatically acceptable.
As I wrote about the whole issue around Nazianzen's commentary on 1 John 5 and grammar:
"Apparently this whole issue was even on the hot table in the 300s, in some form (a whole complex analysis) when Gregory Nazianzen and his grammatical opponents sparred."
Clearly, Nazianzen himself does not seem to be invoking a grammatical argument about the abbreviated text, however it surely looks like others were.
And I am far less convinced that "Gregory does not know of the Comma", especially considering the language interactions of the time. The most that could be said is "unlikely that the Comma was in his Greek mss".Tim Dunkin (note the Knittel ref)
"While it seems that Gregory himself does not know of the Comma, it is also apparent that those with whom he was discussing the passage recognized a grammatical error that is present in the text if the Comma is not included. Knittel notes both the objection to verse 8 offered by Gregory's opponents on the basis of the grammatical solecism introduced by the deletion of the Comma, as well as Gregory's attempt to get around the problem by an effected indifference to the problem. He writes"
Brown has some logic difficulties:
"Gregory .. never suggests that the grammar is incorrect. Thus, Gregory did not invoke the grammatical argument, "
Straw man attempt, obviously.
"meaning that the grammatical argument has no historical antecedent in the ancient church but is a recent development."
Total nonsense and simply illogical. Even the opponents of Gregory looked to be arguing the grammar.
Beyond that, the evidence from extant silence tells us little. The Latins would not make the Greek argument. And the Greeks were not frequently discussing the text. They could not discuss what they did not know.