Do you mean a mobile client dedicated to that style?
I suppose there isn't enough demand for it? Communities are basically like having a Tumblr. Which is quite nice. They could in theory function like subreddits if people decided to use it, client made them more or prominent or the clients who don't even currently have the function, adding it.
But yeah I think I agree. A mobile client that went for the opposite of what they all seem to do now... communities / subreddits as their main format, with the twitter style as secondary would be interesting. Do you think Communities as they are now could do what you want, if they were in a dedicated app?

