From DHH's long-winded keynote at Rails World 2026. He was bragging that Hey's backend is so efficient because it's written in Rust (which he hates and refuses to read).
I don't know about the nazi merch, but this gives a good overview of one of his nazi blog posts https://paulbjensen.com/blog/2025/09/17/on-dhhs-as-i-remember-london/