Wow. This actually hadn't occurred to me before, but I know that I've made minor edits as I've read my own stuff. Mostly it's been for the sake of clarity--replacing a pronoun with a name, tweaking word order, breaking up sentences, etc. As a writer, I certainly wouldn't have a problem with a reader making silent edits of that nature. I'd maybe want a note in the metadata if the edits were in the line of removing or extensively re-working more than a few sentences or a paragraph or two, but I personally wouldn't require permission from the reader (and now I have to go edit my permission statement again ;)).

As a listener, I think I'd prefer changes to be noted at the beginning or in the metadata, not in the actual reading. That said, I can also think of circumstances where audio cues during the story might be helpful, but not outright asides if that makes any sense.

And, yeah, I'd like to know if any major re-writing or re-working was done because otherwise I'd go nuts waiting for favorite parts of the story to happen and be jarred if they happened out of order or not at all.