I can't be the only one who notices this

Yup.
Only I'd say that Karma is slightly more sadistic than Izaya.

in assassination classroom for almost the whole series i could not tell whether or not he was boy or girl it was so freaking confusing until the girls dressed him up to look like a skank to fool a rich boy.

are you referring to voice actors btw?

No, as cool as that would be, they don't have the same voice actor (in the english dub at least), their personalities is what I'm talking about, cute yet secretly psychopathic and just crazy

i did love the glowing eye effect that was given.