Yeah, Carmack has weight due to his history of being incredibly technical and writing lots of incredibly useful code. Also, he has a huge profile in the industry.

He's been a heavyweight proponent of static typing for a while - 2-3 years IIRC - and so it doesn't totally surprise me that Haskell is up his alley. It's particularly notable that he prefers it as a technical lead as a low-pass filter on bugs.