If you go to the Status screen and look at the status ailments, there's this one called 'peerless.' Has anyone ever been afflicted with this? If so, what has it done? Does it say in the book? (I lost my book a long time ago.) Does Sephiroth have it? Those at the beginning of the game, could you check this for me?

It's not a big thing, but it just kind of bugs me.

Peerless is invincible, When attacked under peerless you get '0' damage every turn
Sephi doesn't have it, or at least not that I know..
It only last per battle and can't be casted by some mataria spell. The only way I know it is through Aeris her limits (Earth Gospel .. the 4th and a a 3rd limit as well)

Sephi does have it, during the flash back at Kalm. Thats why Sephi never gets hurt.

That's right, though I believe it is useless to add the status change peerless cuz there is no item or materia combo that can give u that status. The only way to get it is via Aeris'Great Gospel, and that only lasts a few. It'll end when the battle is over so u'll never see it highlighted.

The Shield spell also does that though, I think.