I suggest adding the erasableSyntaxOnly TS compiler option, disabled by default as to not break code. This is dependent on upgrading to TypeScript 5.8, which Deno is soon to do (see #28711). When set to true, this will disallow TypeScript features such as enums, namespaces and class parameter properties, which are non-erasable in Node. In the Standard Library, we made sure to remove these TypeScript features. E.g. Enums in denoland/std#3782.

Related denoland/docs#1608