Hi Christian, thank you for bringing this up! Sorry for the delay in answering, but I wanted to be sure of the technical details of my answer (which won't be short, so apologies for this too).
So, we did consider adding the section metadata as editable wikitext, but ultimately we think there are a lot of potential difficulties with that, and that on the contrary we would have many advantages in keeping it separate.
Conceptually, separating metadata about a document or text from the document itself makes sense. It also allows machines to read and understand it separately. This is the way we did it with Structured Data on Commons, via Extension:WikibaseMediaInfo. It has several advantages, such as:
- the ability to refine user permissions for accessing and editing this type of data, and
- reducing cognitive burden on editors who are not interested in working with this data (as we said in the main page, we don't want to "overwhelm users with too much new content to moderate").
We would also like to try not to complicate wikitext further, by adding additional markup from a technical perspective, because this would create more maintenance burden on a critical piece of the MediaWiki environment (again, we don't want to "introduce too much complexity into our systems").
Also, in the end, information in wikitext is not fully structured data that can be consistently read and understood by machines. We want to ensure that the metadata created by this project will be accessible in a robust, consistent, structured and linked format.
Anyway, I would like to hear more about your reasons why you think it is important that everything be editable as wikitext. Perhaps we can think of other ways to solve those problems.