What you're getting there is how the comment text happens to be stored (and presumably always has been). We've talked about changing that, because it would allow us to do some implementation improvements like... well, I forget just now. Might have had to do with caching. Anyhow, if enough people want it, we'll bump up the priority.
Oh, that's in the actual API.
https://hacker-news.firebaseio.com/v0/item/8422922.json?prin...
I strongly hope they add a plain-text field for returned comments.