We use a variant of git+markdown as well, but it has a problem when non technical people want to contribute to it. Some non technical testers or product people don't know a lot about git or markdown making it non trivial to contribute.
As for markdown, it is so trivial, especially with previews anywhere, that this is a made up problem. I think these "non-technical" people can learn this if needed, and if they have the will.
As a bonus most of them also pick up a basic level understanding of git, which helps them join in other conversations they didn't previously feel they could.