I thought that the author would make the case that technical doc should we written in some semantic format that could then easily be re-processed for various us

I thought that the author would make the case that technical doc should we written in some semantic format that could then easily be re-processed for various use cases which I could sort of understand (although any doc is better than no docs, so if Markdown helps with that I'm all for docs.md). But "my markup language is better than your markup language" is not very productive IMO. The fact that markdown lacks some advanced formatting tools might even be considered a feature, it means that it will render correctly when converted to monochrome output for instance.