Look at the comment under the comment you mention - those issues are about the TS type system, NOT the TS syntax. TS syntax is highly stable, and is the only thing JSR relies on :)
Both `.d.ts` and `.js` files can be created without understanding the TS type system (this is what JSR does). Creating both of those is just a TS syntax transform - one that is highly stable (esbuild and friends all do it already).
