I second that. And if people need to deal with YAML in Python, they should be using ruamel.yaml, which is a far superior library on just about every level: https://pypi.org/project/ruamel.yaml/
Why would I care that the maintainer prefers Mercurial? The document you linked to doesn't say anything about them not taking community submissions: I think you need to scroll down further in the page. And it certainly doesn't say that you have to use SO to submit changes.