Not everyone matures at the same rate, he seems about right for someone his age to me. Maybe.. a bit less stupidly reckless while trying to impress his friends than expected.

[Angeal spent years around adolescent SOLDIERs, his sense of what is normal is badly warped.]

The... catatonia spells aren't really a surprise, if it's any reassurance. It's not my medical history to tell, but as long as he keeps pulling back out of them, it should be alright.

[He sounds extremely confident in that. But explaining why.. not as likely.]

His closeness with his friends will help if it happens again.

[By degrees his tone turns thoughtful.]

Is this really about Sephiroth's experience, or are you worried about someone, anyone taking advantage of Cloud? Maybe even someone he likes?