They are text files. If there is anything weird about them it is that they are indented with spaces and if you are inconsistent with indentation they won’t read into the yaml import function, but I can’t imagine why vim or nano would have a problem with opening them. Maybe the ones you were using were not actually yaml.

Totally lost me. Why the hate on YAML?

This is a false equivalence. The content of the art discussed here has no labels or logos. As soon as you posit the existence of such content, IMO you are in a different conversation.