Problems with the real presence

Usually, arguments about whether Jn 6 and 1 Cor 11 teach the real presence revolve around exegetical considerations. However, that's not the only pertinent consideration:

i) Sometimes reality can serve a hermeneutical role. If the bread or wine just is Jesus, then why doesn't it look like Jesus? The total lack of correspondence between the interpretation and empirical reality is, in itself, a reason to question or reject the interpretation. If it is Jesus, shouldn't it bear a recognizable resemblance to Jesus? 

If I held up a banana and said "This is Marilyn Monroe," the fact that the claim defies manifest reality is good reason to dismiss the claim out of hand. 

ii) Sometimes reality is a check on our interpretations. Suppose a guy shows up on my doorstep tomorrow and announces that he's Jesus. He came back, just like he predicted.

Well, I need to compare that claim against reality. Does he do what Jesus can do. Does it match what Scripture says about eschatological signs when Jesus returns? Certain observable things are supposed to happen in the world that herald his return.

iii) Suppose someone objects that I'm overlooking the miraculous nature of the Eucharist. But one problem with that appeal is that even if we grant the Eucharistic interpretation of Jn 6, Jesus doesn't say it will be miraculous. There's nothing in the text of Jn 6 to indicate that the Eucharist is a miracle–even assuming the Eucharistic interpretation.

Indeed, none of the accounts of the Last Supper in the four Gospels and 1 Cor 11 say the Eucharist is a miracle. The miraculous nature of the Eucharist isn't required by the text, but by a particular interpretation of the text. Appealing to a miracle is an extraneous, stopgap explanation to save appearances for a particular interpretation.