The Markdown-to-HTML conversion for the website uses an internal system. As noted, there are a few discrepancies between the Markdown syntaxes, but the GitHub Markdown previewer and the Colab (Jupyter) preview will get you mostly there.
The generate2.py config script is used to generate the TensorFlow API reference documentation from Python docstrings. This Markdown should be viewable in GitHub and then we convert it to HTML in our docs publishing pipeline. It uses the api_generator module in our tensorflow-docs package. It’s actually a pretty nice Python API documentation system (and not TensorFlow specific), but not really documented. Many prefer it to Sphinx. But, yeah, this is for API docs only and not narrative docs.