Thanks, Marcus. On that CCM paper, I think their approach is great and I'm happy that a whole community of researchers have been working in that direction. With this paper in particular though, it's mightily complex, and I worry that with each step of complexity they're getting further away from good physics. This is often the case with research programs that get popular -- there's a tendency to pile on complications, constructing more and more theory until it becomes a bit of a nightmare. And though I do think this is happening here, at least it hasn't yet gotten as bad as strings.
On the content side, I think I see some of what they're doing, and it is getting closer to my work. Their M_2(\mathbb{H}) \times M_4(\mathbb{C}) algebra contains the su(2) \times su(2) \times su(4) Pati-Salam model, and they're presumably getting gravitational degrees of freedom from the rest of M_2(\mathbb{H}), though I couldn't see quite how in their paper. If that is what they're doing, then they could embed that algebra in spin(4,4) \times spin(8), add their spinor representation and triality, and be looking squarely at E_8.
I do consider them my closest competition. But I'm not especially worried, because my approach is to minimize rather than expand complexity, which is a terrible strategy for building a career but possibly the best for figuring something out.
