If you search for `site:github.com "acme.com"` in Google, you'll find numerous instances of the domain being used in contrived links in documentation as an example of how URLs might be structured on an arbitrary domain and also in issues to demonstrate a fully qualified URL without giving away the actual domain people were using.
This means that numerous links are pointing to non-existent paths on `acme.com` because of the nature of how people are using them in documentation and examples.