Oh, you were meaning the status-blocking thing? I'm not 100% sure myself, I think I threw it on a set-up once in NT and the attack missed. Might have just been a natural miss, but I was assuming it was similar to how Poison works (though that might be hard-coded and unique, like Earth). I also read in one of the FAQs that absorbing an element meant that the statuses it inflicts are actually healed off you instead but I've not tested that at all.
Holy [swear]ing [swear], I don't [swear]ing believe it!!!!! I (we) have just discovered a new way of using Hidden that none of the sources document!!!
Ok, I battled with the Attack Squad, and all of their Smoke Bullets failed to cast Darkness, with perpetual "misses". So I unequipped the Mystile, toned all of my characters down to Lv 15 (and removed all Source bonuses), and gave the players a Lv 1, 2 & 3 Elemental. Guess what? Same result, except the Lv1 Elemental did not nullify Darkness (as you would expect).
So, does this just work with "Hidden" physical attacks, or does it also work with magical attacks too? Over to Nibelheim I went to fight the Dorky faces. YES!!! Not once did Curses or Funny Breath inflict player 2 or 3 with Silence or Confusion. The "miss" sign pops up, which would normally suggest that one is vulnerable but the attack missed, but we all know there are cracks in the coding, and we've just found another one! Nice work!!!!
I'm now going to go on a scavenge to find all "Hidden" attacks in the game, and then I'll do some more tests. My
walkthrough is now going to be getting mulled over I feel, as I know have a much better strategy to offer for at least the Shinra Mansion. I'm excited to see how many other areas Hidden can now be taken advantage of
Oh, and there was no HP restore with the Mastered Elemental. I suspect that only applies when you are Poisoned, as the poison damage has the Poison Element, so you heal yourself every time the poison kicks in.
-edit- I'v just tried it with the Cover Materia too, same result!