>>13201409 Kallen's a surname.
It's also a given name.
Seriously, this isn't even a situation with some bizarre non-existent name (like Gundams "Fllay" and "Ssigh", which not coincidentally were changed into more natural English spellings when the American licensors consulted with the Japanese creators). It's a real name, and it's very clearly deliberate.
Arguing for "Karen" is on the same order of stupidity as people who argue that My-Hime should be called "Mai Hime" despite the very first trailers for My-Hime stating clearly in English that when it's written in ENGLISH, it's My-Hime.
It's like some kind of bizarro reverse Japanophile-ism. I know better than the people who create these things do!