Bukkit

What is the issue?
Is there a way I can do per world prefixes or just per world ranks

Please provide any additional information below.
If so how?

Nope. The only thing that can be per-world (or per-region) are permissions.

Everything else is global/universal.

Per-world metadata (which includes prefixes) may come eventually.

Per-world groups... probably never without a major rewrite.

@ZerothAngel: Go

Can i not set different weights per world for ranks?

@DanSpedey: Go

The groups are global/universal, so their weights are as well.