I think that’s a good visual definition of transclusion: when you are reading a quote and suddenly Ted Nelson appears, staring back at you—that’s transclusion.
I don’t know if this is a good idea, but I imagined a "scroll bar" appearing as the source text is revealed, orienting you within the total text… I was too lazy to make an animated GIF, which I know is becoming the CDG standard; here is a three-page PDF you can flip through to see what I mean. The scroll bar “track" is actually the entire text; the “thumb” is the amount of text currently displayed in the full-sized quoted area.