I find this quite the coincidence because I had a short discussion about this subject earlier. Also, I do think there is a lack of human diversity in role-play. Not just on Feral Heart, but other platforms also. Usually, in my opinion, taking to playing a diverse character is all about being your character and telling the story. For example, if you play an African American character, don't just simply use bad grammar or be a Mexican and put "o" at the end of every word you say. That would be stereotypical and some people could find it offensive. Yes, it's for play, but some people may take it the wrong way.
Though I'm classified as an African American, myself in terms of real-life, don't simply take into the idea of diversity for that alone. I take to the idea of diversity because humans are very diverse themselves, like dogs and the other animals we like to play everyday. If the animals can be diverse when role-playing, why not human characters?