The private messaging idea was thrown around many times, it's useful and can (should) be implemented off-chain. If that's the intention of steempeak, go for it :)

My first impression is, it's a sleek interface but the posts are too big, maybe reduce the image sizes and show more posts in the field of view. The "detailed view" is a little bit chaotic: the animated reshuffling is cool, but the posts end up looking disorganized to my taste.