I don't think the post is bragging about this. It's well known amongst the Rust community that this stuff is pretty easy to do)

I read it as a primer for writing simple Rust programs that can run baremetal on the Pi (I've cross compiled for a Pi-with-OS before but never tried this) and access GPIO.

If you're talking about the HN upvotes, HN just tends to upvote posts mentioning Rust a lot :)

Have you looked at https://zinc.rs/?