These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Let's just put it this way: you know FF:Mystic Quest? The game with the amazing soundtrack? Yeah, one of the two composers of that game, Ryuji Sasai, the one that composed the kickass Doom Castle and Dark King melodies for Final Fantasy Mystic Quest, wrote the music for this game.
Game Breaker: Whoever translated the rom into English inadvertently made it so that certain mantras can cast ultra powerful spells for 1 MP. If you stumble upon them by rewriting your own mantras, or just get them off a FAQ, you'll have a few nice Disc One Nukes and won't have to worry about physical combat for a long while.
Good Bad Bugs: When the three teams reunite with Dune and the fourth chapter begins, the game does not transfer the characters as they last were when you used them, but rather "remembers" how they were at the end of their respective chapters. This means that if you complete Sion's chapter last and unequip the Hercules Armor afterwards, you'll get a copy of it to give to Dune.
Another one that might not be a bug, although it certainly seems to be: there's a room near the end of the game that contains four treasure chests, each containing a monster-in-a-box and a Magic Leaf. You can enter this room as many times as you like, and the magic leafs will respawn every time, allowing you to max out everyone's MP.