In chapter 4 of his excellent Interpolations in the Pauline Letters, William O. Walker discusses the different types of evidence for interpolation. He subdivides the ‘Contextual Evidence for Interpolation’ category into three subcategories:
a) Conceptual, Stylistic and/or ‘Tonal’ Interruptions of the Context
b) Repetition of Significant Word or Phrase
c) Apparently Insignificant Textual Variants.
In this first subcategory, with ‘tonal’ as a synonym for ‘emotional’, only 1 Corinthians 14:34-35 is mentioned, the removal of which ‘leaves a complete and coherent discussion of spiritual gifts in chs. 12 and 14’. (Interpolations, p. 74).
I was rather surprised with this conclusion, as in 1 Corinthians 12 there is also a section that has, in my opinion, a completely different emotional quality than the surrounding verses. Verses 2 and 3 seem to be the work of an angry interpolator, and his anger appears to be directed at gentiles who had (recently?) been converted to Christianity, because these new converts curse and glorify inappropriately. This angry reprimand has nothing to do with the calm and rational discussion of the spiritual gifts in the rest of this fragment. Moreover these two verses interrupt the flow of the text. Verses 1 and 4 connect quite naturally, verse 1 being the introduction, verse 4 the start of the explanation.
(1) Now concerning spiritual gifts, brethren, I do not want you to be uninformed.
(2) You know that when you were heathen, you were led astray to dumb idols, however you may have been moved. (3) Therefore I want you to understand that no one speaking by the Spirit of God says “Jesus be cursed!” and no one can say “Jesus is Lord” except by the Holy Spirit.
(4) There are varieties of gifts, but the same Spirit; (5) and there are varieties of service, but the same Lord; (6) and there are varieties of working, but it is the same God who inspires them all in every one. (7) To each is given the manifestation of the Spirit for the common good. (8) To one is given through the Spirit the utterance of wisdom, and to another the utterance of knowledge according to the same Spirit, (9) to another faith by the same Spirit, to another gifts of healing by the one Spirit, (10) to another the working of miracles, to another prophecy, to another the ability to distinguish between spirits, to another various kinds of tongues, to another the interpretation of tongues. (11) All these are inspired by one and the same Spirit, who apportions to each one individually as he wills.
Clearly, 1 Corinthians 12:2-3 should be added to the long list of interpolations in the Pauline letters.