Damn, that's a shame. I started playing Zestiria over the week-end and decided to give his mod a shot last night and holy shit, it makes a world of difference! I regret not installing it sooner and I'm only five hours in.
Hopefully he'll reconsider but, honestly, even if he doesn't I don't blame him one bit. The Steam forums are just awful. Really not worth interacting with in general.