Thank you for replying, mwh, Markos and jeidsath!
In my response I will try to cover all the points that have been addressed. I will also add another thought (point D), which I would like to hear your opinion on.
A) Theology
I view the bible as God´s word and its authors as inspired by the Holy Spirit. That is also a reason, why - despite internal arguments such as vocabulary/style - I reject the idea of the Pastoral Epistles being pseudepigraphy. There are of course arguments for such a conservative view of Pauline authorship (style/wording could come from an amanuensis), but they have been explained well by others, e. g. Daniel B. Wallace. Jeidsath, what do you think the bible is?
Due to my evangelical beliefs, I try to understand it as well as I can and simply do what it says. That is my only “agenda”. I am not personally interested in feminism, anti-feminism, pentacostalism, anti-pentecostalism or any other theological programme. And this is also the reason, why I have asked my question here. I stumbled across the feminist approaches toward 1Cor 14:34-36 and, even though they appeared to be very dubious, I wanted to hear some Greek scholars on the matter.
B) 1Cor 14:34-36 - Insertion?
Due to the controversial content of these verses, this view has attracted many theologians. jeidsath has mentioned, that it would have to be a very early insertion, which I agree with. After all, it appears in all manuscripts without a single exception.
C) 1Cor 14:34-36 - Quotation from the Corinthians?
As mwh and jeidsath have said, there is no basis for the theory - I have not found the slightest indication of these verses being a quotation, rather than Paul´s word. Some have tried to understand the ἢ as indicating it, but as Markos has put it, the ordinary meaning fits the context and trying to make the ἢ look as an exclamation of astonishment seems far-fetched and desperate.
D) Internal Argument Against the Interpolation Theory
I want to come back to the insertion idea. Actually, I think taking out the verses disturbs the flow of the text:
ὡς ἐν πάσαις ταῖς ἐκκλησίαις τῶν ἁγίων,
34 αἱ γυναῖκες ἐν ταῖς ἐκκλησίαις σιγάτωσαν, οὐ γὰρ ἐπιτρέπεται αὐταῖς λαλεῖν· ἀλλὰ ὑποτασσέσθωσαν, καθὼς καὶ ὁ νόμος λέγει.
35 εἰ δέ τι μαθεῖν θέλουσιν, ἐν οἴκῳ τοὺς ἰδίους ἄνδρας ἐπερωτάτωσαν, αἰσχρὸν γάρ ἐστιν γυναικὶ λαλεῖν ἐν ἐκκλησίᾳ.
36 ἢ ἀφ᾽ ὑμῶν ὁ λόγος τοῦ θεοῦ ἐξῆλθεν, ἢ εἰς ὑμᾶς μόνους κατήντησεν
To me it appears that verse 36 leads us back to v. 33b. ἐν πάσαις ταῖς ἐκκλησίαις they are doing it, so you should do it, too, ἢ εἰς ὑμᾶς μόνους ὁ λόγος τοῦ θεοῦ κατήντησεν? V. 34-35 really seem to be embedded here. Why would he say has it come to you alone, if he was not contrasting them with all the others (all churches of the saints)?
If we delete the verses we end up with:
31 δύνασθε γὰρ καθ᾽ ἕνα πάντες προφητεύειν, ἵνα πάντες μανθάνωσιν καὶ πάντες παρακαλῶνται,
32 καὶ πνεύματα προφητῶν προφήταις ὑποτάσσεται·
33 οὐ γάρ ἐστιν ἀκαταστασίας ὁ θεὸς ἀλλὰ εἰρήνης.
36 ἢ ἀφ᾽ ὑμῶν ὁ λόγος τοῦ θεοῦ ἐξῆλθεν, ἢ εἰς ὑμᾶς μόνους κατήντησεν;
I do not see a logical connection between verse 33 and verse 36.
All that being said, I have to agree with mwh. Paul´s words are rather plain and painful for the modern ear. Some have tried to connect it to the preceeding context of prophesying. Paul then would have wanted to say they should not prophecy or evaluate prophesy. But he simply forbids to speak. I do not think that Paul hated women, because he had some very appreciating words for women, e. g. in Romans 16. I do think, however, that he believed that there were some clear restrictions, such as not speaking in church. 1Timothy 2:12 is not as strict, since εἶναι ἐν ἡσυχίᾳ could mean a quiet demeanor, but οὐ γὰρ ἐπιτρέπεται αὐταῖς λαλεῖν is really quite “hardcore”. σκληρός ἐστιν ὁ λόγος οὖτος· τίς δύναται αὐτοῦ ἀκούειν;