[KuraFire]

*nods*

boofo, what's important here is this:

try picturing the structure of your forum - a post is defined by someone's user id - after all, you can easily change their usernames in your admin panel, and that doesn't affect their posts or anything.

Now try picturing what would happen if suddenly their user ID would be changed. How else would the system, vBulletin, know which post belonged to them, and which didn't?

Do you see the conflict there?