I think that just shows LLMs are great at almost any language. As the post says, it can get very poor, as with J and Factor, but anything remotely easy to read for humans seems to be perfectly fine for LLMs. I can say I am still to try a language they struggle with myself. Tried Dart, Groovy, Common Lisp, Elisp… and more. It is an expert in all of them and I can’t really tell they advantage one over another. Our mixed Kotlin Java huge code base is a walk in the park for Opus5 and Fable5.