Quotation marks?

We're going through 1 Corinthians, and I suspect several things would have been much clearer -- all along -- if Koine Greek had had quotation marks. The letter was written in response to a letter from them ("Now concerning the things about which you wrote"), and also presumably in response to a report from "Chloe's people" who I guess brought the letter to Paul. (The postal service was for the Emperor and the army.)

The very next clause in 7:1 is "It is good for a man not to touch a woman." I find it a little hard to believe that the scholar Paul would have so forgotten about the first recorded commandment as to make such a blanket claim.

Likewise in chapter 10 he makes the provacative statement "All things are lawful", which seems to flatly contradict his statements in chapters 5 and 6 detailing unlawful things.

The difficulties vanish if he is quoting the Corinthian elders' letter. I'd suppose that they, in reaction to the moral atmosphere(*), made the extreme claim about sex, probably buttressed with examples as to why. And they explained their reasoning for allowing Christians to eat meat sacrificed to idols -- offsite. So I think of the text as containing quotation marks, and Paul is arguing against their application of the claim on their own terms.

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(*)"To corinthianize" may refer to the Greek Corinth, destroyed by Romans in 146BC and rebuilt as a Roman city in 44BC. Or maybe both cities.