Upgrading a standard account to a CE account

[Nekodar]

So I can upgrade a standard PC edition with a PS3 CE box, but not with the PC CE box? That's retarded.

It's possible between PS3 and PC because they're different platforms. Just like you can't register two PC codes to one service account, you can also not register two PS3 codes to one service account.
If it was not possible to register different platforms onto one service account, people wouldn't be able to play on PS3 and PC with the same service account.
Retarded or not, that's how it works.