@strypey@liamdiprose@hobs Right. I've used source control products to collaboratively write documents in LaTeX, so I'm philosophically sympathetic to the suggestions being made here, but I don't think they're really appropriate for the use case described in the OP.
LaTeX is great, but it has a steep learning curve and is not widely known outside of certain STEM fields (and even then it seems to mostly be used among researchers).
Source control tools are probably the most powerful solution for collaboratively editing documents, but they also have a steep learning curve and are not really known by non-programmers. I've even had issues getting STEM folks to really wrap their heads around it.
While you can use an issue tracker or similar mechanisms to track meta-discussions among authors, this is, again, not the natural way people are used to doing this if they are not programmers.
It sounds like the intended use case is to have collaboration with a wide range of authors, which seems to make the foregoing deal killers (unless they're all scientists who write code or something).
I'm guessing some of the suggestions like asciidoc or pandoc are a bit more on target, but a solution that presents more user interface for contributions and comments seems more ideal. I don't have a strong suggestion, but I did think about Wikibooks as one possibility (but not necessarily the best one). I think that just uses MediaWiki but maybe with some specific customizations.