Seifer didn't believe in ghosts.
(It was bullshit - the reason was that he had enough trouble without having to take orders from Squall, and he'd gone into Garden one night to tell him that. No ghosts as far as he could see.)
Still, even if there weren't any hauntings at Garden, people were happy to spread rumours that there were. There was a ghost following Zell around, Raijin told him one night over dinner. It followed Zell on his missions - one time, it grabbed the papers Zell was supposed to be delivering after he knocked himself out and got em where they were supposed to be; one time him and Quistis found a sniper in the hotel across from theirs with his throat cut. No one ever really saw it. It was just a white shape on the edge of their vision, one that vanished before they could even turn around. Zell never said anything about it - and Seifer had snorted at that, wanted to know when Zell ever managed to keep his mouth shut about anything - but if it was making his life easier, no one would expect him to complain.
Seifer laughed at the story - he laughed at most of the stuff that came out of Garden, especially the new SeeD. He'd been called a lot of things, before and after the Sorceress, but that was the first time anyone had called him a ghost.