What effect did the 1897 decree regarding the Johannine Comma have on Catholic scholarship?

Question

The Comma Johanneum, found in some versions of 1 John 5:7–8, such as the KJV, is a disputed text that has been used since at least the Middle Ages to defend trinitarian doctrine. Scholars now widely consider it to be a later addition to the text, but this was a subject of significant debate in previous centuries. The Catholic church took notice in 1897, and apparently applied some sort of restriction on allowable positions within the church:

The Catholic theologian [...] cannot pass over the disciplinary decision of the Holy Office (13 January, 1897), whereby it is decreed that the authenticity of the Comma Johanninum may not with safety (tuto) be denied or called into doubt. This disciplinary decision was approved by Leo XIII two days later. Though his approval was not in forma specifica [...] all further discussion of the text in question must be carried on with due deference to this decree. (Catholic Encyclopedia, Epistles of St. John)

According to Wikipedia, this state seems to have ended in 1927, when Pope Pius XI decreed that the Comma was open to dispute. I'm trying to better understand the practical implications of the 1897 decree during the 1897–1927 period. In that vein I'll pose the following (hopefully indicative) questions:

• Around the time of 1897, what did the phrase "with safety" mean? For example, did it imply the possibility of excommunication or loss of salvation? Or perhaps simply that rejection of the Comma was a sin?
• Did the 1897 decree provide specific guidance regarding what kind of "calling into doubt" was not permitted?
• Presumably direct statements would be included, like saying "The Comma is not authentic," but what about publishing research that could be interpreted as suggesting inauthenticity?
• Are any Catholic theologians known to have been punished for violating the 1897 decree during this period?

Wikipedia includes a note that the 1927 decree clarified that the original decree was not meant to stop "moderate and temperate" investigation by scholars who promise to accept the Church's authority. Be that as it may, I'm not convinced that that's how the 1897 decree would have been understood prior to the 1927 decree, so I'm focusing on how it was originally (perhaps mistakenly) interpreted and applied.

Answer 1

Fr. Réginald Garrigou-Lagrange, O.P., discusses this in the introduction (§ "New Testament Testimony On The Three Persons") of his The Trinity & God the Creator (1952):

The second text of St. John referring to the three persons together is the famous Johannine comma: "And there are three who give testimony in heaven, the Father, the Word, and the Holy Ghost. And these three are one" (I John 5:7). A great controversy has arisen about the genuineness of this text. Those who attack the text argue from the fact that it is not found in any Greek codex of any authority, nor in many Latin codices and versions. From this they conclude that this "comma" was originally a marginal note which in the course of time was incorporated into the text. Consequently the text would enjoy only the force of tradition. The defenders of the text say that it was always in the Latin version, which is more ancient than the Greek codices, for it is found in many Latin codices and is cited by many of the Fathers, by Tertullian, St. Cyprian, and St. Augustine. The omission of this verse in the Greek codices is explained by the fact that the seventh and eighth verses begin and end in the same way and thus the scribes could easily have omitted the seventh verse. In the Latin version the seventh verse is: "And there are three who give testimony in heaven, the Father, the Son, and the Holy Ghost. And these three are one." The eighth verse is: "And there are three that give testimony on earth: the spirit, and the water, and the blood: and these three are one."

On this matter the Holy Office has issued two declarations.[Denz., no. 2198] In the first, dated January 13, 1897, we read:

The authenticity of this text of St. John cannot be safely denied or called into doubt.

Later, on June 2, 1927, the Holy Office declared:

This decree has been issued to repress the temerity of those private teachers who have attributed to themselves the right of completely rejecting this 'comma' of St. John or at least by their final judgment of calling it into doubt... . It is in no way intended to deter Catholic writers from investigating the matter more fully,... or from adopting an opinion opposed to the genuineness of the text, as long as they profess to be willing to submit to the judgment of the Church, to whom has been committed by Jesus Christ the duty not only of interpreting the Sacred Scriptures but also of guarding them faithfully.