When someone is mentioned using `@username` syntax, there are already some cool things happening, like showing user-vcard on hover and sending that user an info.
It would be even more easy to use, if it would propose matching usernames after the first ... say: 3 letters of a name have been typed; just like the `Assigned to` or `Projects` fields do.
Sure, for nicks like `Judge` there isn't much value in this; but if a user is named `thisisthelongestnickicanthinkof`, this comes in very handy.