The point is that you can create a rich text editor that stores the data as markdown.
Note how I said that git and markdown could be abstracted away, as in hidden from the user who can’t be bothered to learn. Use them under the hood, so at the end of the day your entire wiki is just a repo.
> The point is that you can create a rich text editor that stores the data as markdown.
Both Nextcloud and XWiki do this.
Now, why not git+markdown? I'm not sure it exists so we can't really know if it can work well or not.
I have my doubts:
About Markdown: I believe it is fine for very basic content, but you will probably want something more powerful to cover more advanced needs. HTML will be too low level for this, so you will probably need something to extend Markdown with custom macros, at which point you may as well adopt something that already exists.
For git: wikis tend to have versioning per document, not of the whole stuff. You will want to have easy and efficient document history manipulation (access of old revisions, comparison between revision, rollback). And you may want the wiki to remain efficient with a large number of documents and revisions, even when multiple people are writing to the wiki at the same time, and the git repository might be a bottleneck.
For a single user with simple note taking needs, I believe git+markdown can have good characteristics. I'm not sold on the git+markdown thing for a multi user wiki. It would need to be proven, but should someone do this, they should not solve "How do I write wiki software based on git+markdown", the problem should be "I need to have a wiki that's efficient in such and such cases, and git+markdown is a good basis because [...]".
Note how I said that git and markdown could be abstracted away, as in hidden from the user who can’t be bothered to learn. Use them under the hood, so at the end of the day your entire wiki is just a repo.