Marking authorship in texts

While writing something about Wikipedia, and talking about the idea of tracable attribution of text, I’ve been thinking of ways in which works with multiple discrete authors have displayed the different contributions of those authors.

At one extreme, there’s a fully “collaborative” work – no-one makes a distinction between the two authors, and while they’re named on the title page the writing is implicitly attributed to both. At the other extreme, we have individual chapters or articles – A writes chapter 1, B writes chapter 2, etc., and they may never have known of the other contributors.

In the middle, there’s cases where the work is broadly collaborative but with individual elements – the main text is jointly written, but particular contributors sign their own footnotes, sidebar sections, forewords, appendices, etc.

The one that interests me, though, is something I saw in I.S. Shklovsky’s Intelligent Life in the Universe when I read it as a student – I seem to have lost my copy in the intervening ten years, so this is from memory.

The book was originally published in the USSR in the early 1960s, and translated and expanded in English with the aid of Carl Sagan later in the decade. The original text was updated by Sagan, who also added several new chapters; the two then shared drafts, editing “each other’s” sections. Given the political climate, however, they were keen to avoid claiming to be in agreement on some sensitive topics, and so they experimented with explicitly marking the appearance of a single voice in the text itself.

In the end, the result ran something like:

Lorem ipsum dolor sit amet, consectetur adipisici elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. ▲Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.▼ △Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.▽

Unmarked text was jointly written; black triangles marked remarks by one author, and white triangles by another. (At at least one point, delightfully, they started arguing.)

So, the question: was this something common in the period that I’ve just never noticed elsewhere? Is there a name for it? What other novel ways of marking authorship have been used?