I think there's such a thing as over-clustering, it gives your work a very notable "blocky" look I took to be an intentional stylistic choie. It looks nice, but don't hard-lock yourself into it! I've always taken clustering as less of a hard rule and more a heavy recommendation, personally. There's some details you can't really compress like that! Notable on this would be the curvature of Louie's round, sad, bald head. The square highlight would serve to better indicate the curve of his face.
Here, I've tweaked a couple of the faces so they're less squinty while still taking clusters into consideration. I didn't mess with the shading stuff I mentioned earlier, but hopefully it gives you ideas!