Regarding HQ4X, they used the algorithm to create 4X image but used Nearest neighbor to create 8X and 16X images. I think doing HQ4X two times would have result

Regarding HQ4X, they used the algorithm to create 4X image but used Nearest neighbor to create 8X and 16X images. I think doing HQ4X two times would have resulted into a better 16X images without jags.