README.md files and more are pretty common to store in source control because they generally work better in line-differencing environments than most other formats. However, adding a word to a line and reflowing a paragraph still results in more noise than actual, functional difference between the content with traditional differencing tools. Using the CommonMark AST, differences would be far less noisy.
Caleb Baker commented
An interface built into the GUI that would allow the user to view/author README.md files (with the right permissions) without the need to copy down the file or repo locally would amazing.