I love EDN (especially the integrant extensions) for configuration of the stack — that is, dependency injection and so on, the developer-focused configuration.

For user-facing configuration I still favour TOML. I think it’s a bit application dependent, sone applications (eg nginx) have complex configuration needs and for that it makes sense to use something more sophisticated, but for many user-facing config settings, a simpler-TOML would be a great fit. Basically just some basic key-value pairs that can be collected into groups. As the article states, the parsing types should perhaps be enforced by the parser not the written config.