It's a shame to see that comment getting modded down. It's absolutely valid and correct. The three examples given in that other comment are pretty much unknown. xmonad might be a slightly better example, but it's still pretty much unknown, too.

While Haskell has seen some usage, of course, we really haven't seen any major and widely-used non-compiler software developed using it. It's perfectly legitimate to point this out, and using very obscure counterexamples doesn't change this reality.