> Just add the ability to ask for pull requests, to comment, etc into git
That's a major understatement. To "just" add this into mainline git, you'd essentially need to either fork git itself in order to add these features or figure a way to add this without making breaking changes, and then convince git maintainers that your PR is worth adding, and then convince enough people to actually use this new standard in place of what they already have (which will also need them to integrate this with their existing forge infrastructure to mitigate XKCD Standards).
That's a major understatement. To "just" add this into mainline git, you'd essentially need to either fork git itself in order to add these features or figure a way to add this without making breaking changes, and then convince git maintainers that your PR is worth adding, and then convince enough people to actually use this new standard in place of what they already have (which will also need them to integrate this with their existing forge infrastructure to mitigate XKCD Standards).