PM: If the epigraph's meaning/feeling/sensation
suffuse the poem, then it is IN the poem.
JF: If the epigraph is IN the poem, then it is not an epigraph.
As for metaphor, I think the metaphorical should be an extension rather than
a contradiction of the literal. There is such a thing as bad metaphor. Viz,
Carole Anne Duffy's 'my feelings [or whatever] run like paint in the rain'
strikes me as hideous, for if paint ran so there should be many more (and
much wealthier) painters.
JF>That is because the attachment of an epigraph is a critical act.
>PM Secondarily yes. Primarily it is a creative act.
I believe it is an act at once critical and creative. See TSE, 'The Function
of Criticism', 1923.