This question has intrigued me for a while now, and so far I have found the following points that are relevant.
Textual History
First, according to the history of the NA text, "In 1898 Eberhard Nestle published the first edition of his Novum Testamentum Graece." I have tracked online an 1899 copy that had all the commas. This was still true as of 1923, which was soon before the next phase when "Eberhard Nestle’s son Erwin ... provided the 13th edition of 1927." So it was not divided that way in the early NA text.
Second, at least since NA26 it has been divided as three triads, assuming that the statement holds from NA26 to NA27 (I have an NA27 and confirmed it also had three triads like NA28; I do not have NA26):
The text of this edition is identical to that of the 26th edition, but
the critical apparatus and the appendices have been thoroughly
revised.
I have not been able to find enough online sources (nor do I currently have easy access to other sources) to track the various editions to see where the change occurred between 1923 and 1975 (UBS 3rd ed., which was the text of the NA26 published in 1979 [see again here]).*
* If anyone knows of some online sources of the NA text 13th through 25th edition, please let me know.
Influence?
As best as I've tracked so far, the earliest reference to a division is in J. B. Lightfoot's commentary St. Paul’s Epistle to the Galatians in 1870. He states of v.22-23 (emphasis added):
The difficulty of classification in the list which follows is still
greater than in the case of the works of the flesh. Nevertheless some
sort of order may be observed. The catalogue falls into three groups
of three each. The first of these comprises Christian habits of mind
in their more general aspect, ‘love, joy, peace’; the second gives
special qualities affecting a man’s intercourse with his neighbour,
‘long-suffering, kindness, beneficence’; while the third, again
general in character like the first, exhibits the principles which
guide a Christian’s conduct, ‘honesty, gentleness, temperance.’
Lightfoot's ideas have been used in later commentaries:
- Quoted directly by a contemporary, John Peter Lange in his A Commentary on the Holy Scriptures: Galatians in 1870.
John F. Walvoord and Roy B. Zuck, Dallas Theological Seminary, The Bible Knowledge Commentary: An Exposition of the Scriptures (Wheaton, IL: Victor Books, 1985) are definitely influenced by Lightfoot's thoughts, though they do not explicitly credit him, so they may have picked up the ideas elsewhere without realizing the source. They state (emphasis added):
The first three virtues are habits of mind which find their source in
God. ... The second triad reaches out to others, fortified by love,
joy, and peace. ... The final three graces guide the general conduct
of a believer who is led by the Spirit.
Noted in Timothy George, Galatians, Vol. 30, The New American Commentary (Nashville: Broadman & Holman Publishers, 1994), where he states (emphasis added):
Paul grouped these nine graces into three triads that give a sense of
order and completion, although here too there is no attempt to provide
an exhaustive list of the Christian virtues:
Love, joy, peace
Patience, kindness, goodness
Faithfulness, gentleness, self-control.
Various interpretations have been given about the meaning of this
threefold structure of threes. Three, of course, is the number of the
divine Trinity, signifying in this case the perfect unity and loving
reciprocity that has existed from all eternity among Father, Son, and
Holy Spirit. Lightfoot suggested the following categorization of the
nine graces: the first three comprising habits of the Christian mind,
the second reflecting social intercourse and neighborly concern, and
the third exhibiting the principles that guide a Christian’s conduct.
More simply still, J. Stott has described this list as a cluster of
nine Christian graces that portray the believer’s attitude to God, to
other people, and to himself.
Note that he mentions John Stott as well, of which n.94 associated to the statement above references Stott's work "Only One Way, 148". That note also says to see "the excellent article and literature cited in D. S. Dockery, 'Fruit of the Spirit,' DPL, 316–19." I believe DPL refers to: Gerald F. Hawthorne and Ralph P. Martin, eds., Dictionary of Paul and His Letters, (Downers Grove, Ill.: InterVarsity, 1993); so that may contain more thought about the triads.
Conclusion
So it appears that Lightfoot's triad ideas (if such is indeed original to him) influenced someone involved with the Nestle-Aland text editing after 1923, such that the editions began to reflect this triad idea in the Greek text punctuation as you have seen in the NA28 text.
There is nothing I am aware of in the Greek or the context of Galatians itself to necessarily consider them in the triad Lightfoot sees. His observation is merely that, and it seems a leap to actually codify that into the textual punctuation itself.
