My problem with updating Matter Overdrive in Horizons is that it forces people to use Java 8 - and not just any Java 8, either. We've established that
Galacticraft doesn't even work with OpenJDK 8, meaning that we'd be forcing people to go with Oracle. We have stated before that we don't support non-oracle java versions and that we're trying to move away from Java 7, but I'm not sure I'm ready to restrict people that much.
That said, there are a large number of issues involving Matter Overdrive that were fixed in the update - quite a few critical ones that determine whether the mod is usable or not. I think at this point I'm faced with either removing it or forcing people on to Oracle Java 8, and I'm not sure which to do. I do love Star Trek.