One way that this [discussion about writing down a new shared standard for recent Haskell developments] has come about, is that the compiler I am responsible for (the GHC or Glasgow Haskell Compiler), has become the de facto standard. There are lots of people using that, so if you use GHC then your program will work.
I don’t think that’s a good thing in principle, however, for a language to be defined by an implementation. Haskell is based whatever GHC accepts right now, but it [Haskell] should have an independent definition. So I would like to see Haskell Prime [their upcoming language spec] happen because I think it’s healthy to see an independent definition of the language rather than for it to be defined by a de facto standard of a particular compiler.
I've seen it over and over -- no matter how well-intentioned the stewards of a standard are, when you only have one implementation you end up getting tied to unintentional details.