Of course it matters even if YOU don't want to participate. The techy types that frequent here may actually want to contribute, or be interested in how the code was implemented as a learning resource.
Additionally, there are biased for and against programming languages, and I guarantee that there is a whole set of people on HN that would be interested in this project because it is a language they like. Rust means you can run this software almost anywhere and it's going to be easy to install.
To be honest I'm slightly annoyed whenever a github submission mentions the programming language for no specific reason.
Rust is a great tool but it doesn't matter unless you want to participate in this project.