Happy Fable user here.

I think it´s easy to find some feature of a language (such as modules) and claim that every language without it is not viable. You could make the same claim about OCaml not having some of F#s best features, such as operator overloading, inline and computation expressions. But this misses the point. If you´re writing a functional-first web application, then the F# solution and the ReasonML solutions are going to look very similar.

Regarding server run-times and Microsoft lock-in, this is no longer an issue. DotNET Core is open-source and cross-platform. You can also use Fable to compile F# code for Node.

I'm not claiming F# is not viable without the module system, I'm saying F# is not a drop-in replacement for OCaml. There are good reasons people might prefer OCaml. I that that's a reasonable response to this comment:

> I don't understand the Reason hype when F# / Fable already offers this

My only point is that there are good reasons people would prefer ReasonML/OCaml over F#. I never claimed there were no reasons other people might prefer F#.

> DotNET Core is open-source and cross-platform.

The only open-source debugger available for .Net Core is a poorly implemented hack by Samsung, because the vendor-provided debugger was never open-sourced.

https://blog.lextudio.com/the-rough-history-of-net-core-debu...