This is because mori is written in ClojureScript. For the most part, all mori is doing is exporting pieces of Clojure so that the native JavaScript environment can access them[1]. In Clojure, the naming convention is "foo-bar", and the cljs compiler translates that to "foo_bar".
I can't imagine changing the cljs compiler or adding a piece to mori that must be maintained is important enough for this. I'd imagine Swannodette's answer would be "you should use ClojureScript anyway" :)
I don't think it'd be a huge issue in any case, probably just a case of providing a handler for name conversions. Not sure if it's worth the extra code lying around, but anything that potentially makes cljs a better actor in the js world is nice.
I can't imagine changing the cljs compiler or adding a piece to mori that must be maintained is important enough for this. I'd imagine Swannodette's answer would be "you should use ClojureScript anyway" :)
[1] -- https://github.com/swannodette/mori/blob/master/src/mori.clj...