The best proof of the existence of someone as Marcion

[Giuseppe]

the so-called Hymn to Charity of 1 Corinthians 13 was probably interpolated to eclipse the embarrassment for the glossolalia episodes described just before in the same epistle.

But that hymn is so beautiful that it is the best proof of the historicity of someone as Marcion. Who could interpolate it in the epistles, if not Marcion or one very similar to him?

[Benway]

Literally anybody who appreciated good writing? The inclusion of any of the badly written or controversial interpolations would be a better argument for the need of an authority figure to enforce their inclusion than a chapter which people would accept anyway.
In any case, the evidence that Marcion edited the epistles is pretty flimsy as they disagree with his beliefs too much. Why would he leave in the part about women being forbidden to speak in church when the Marcionite church had women as priests?
Somebody else compiled the 'Marcionite' Pauline epistles and the Marcionites adopted them at some point.

[Giuseppe]

In any case, the evidence that Marcion edited the epistles is pretty flimsy

The gnostic terms used by Paul may betray marcionite interpolations. This would imply that Paul was not a gnostic, but Marcion (obviously) was one.

Assume for a moment this last scenario: a not-gnostic Paul interpolated by Marcion before and then by catholics.

In Acts, Paul receives an apostle-assistent: Nicolas. The same Nicolas hated so strongly by the book of Revelation, where the Nicolaites are probably gnostics.

Hence, even if Paul was not a Gnostic, he was perceived as influenced by the gnostics.