I don't understand why transclusion has to be so hard.
Any developer can probably implement it on the web in a weekend by adding some metadata to some <blockquote> tag and creating a browser extension that displays the source page on the side, locate the copied text in it, and scroll to it.
Heck, you probably could brute force it by doing a Google search for every <blockquote> or "some text" patterns in a document, and link to whatever is the #1 result.
Any developer can probably implement it on the web in a weekend by adding some metadata to some <blockquote> tag and creating a browser extension that displays the source page on the side, locate the copied text in it, and scroll to it.
Heck, you probably could brute force it by doing a Google search for every <blockquote> or "some text" patterns in a document, and link to whatever is the #1 result.