See now private interpretation seems to be saying to you something different than what that passage says to me. You seem to be suggesting that Paul is using "we" as in "we scripture writers". I don't see that, he is talking about letters he has written to the Corinthians not scripture in general.
You're not alone. Others have trouble with his stuff, too.
2 Peter 3:15-16
15Bear in mind that our Lord's patience means salvation, just as our dear brother Paul also wrote you with the wisdom that God gave him. He writes the same way in all his letters, speaking in them of these matters. His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction.