In my copy of the United Bible Society's Greek New Testament, the preface says that square brackets "in the text enclose words whose presence or position in the text is regarded as disputed ...."
In Cor 13:4, the words he agape ("the love") occur three times. The last of these is enclosed in square brackets in my UBSGNT. Still, all editions of the Greek New Testament include the disputed words except, of course, Westcott and Hort's text.
Now look at the apparatus in my UBSGNT:
The omission of he agape is supported by only one Greek uncial manuscript, which is Codex Vaticanus (B), a manuscript that Hort consistently felt represented the original text in places of textual variation. One of my textual critic friends sometimes refers to the "hypnotic effect and Aleph and B." Here is a classic example. There is very little possibility that the reading of B here could be original, and, in my opinion, square brackets should never have been placed around these words. A simple footnote would have sufficed.
I have so much to say about this but I'll save it for my my chapter on textual criticism in my book on interpreting the New Testament.