As everything I know about nitro coffee I learned today I can hardly offer up myself as an expert on the subject but from what I have read today it would seem that the basic principles that make stout foam what it is would apply to coffee treated similarly.
I note from a couple of the web articles that I read this morning that CO2 is sometimes used with coffee. It is always used, of course, with Guiness - perhaps because that carbonic prick is desired with beer.
Thanks again! The carbonic bite doesn't go well with coffee (some kind of undesired bitterness/sourness). That's why people recommend 100% nitro. And even with pure nitro they're getting creaminess and the cascade effect!