I doubt that's possible.
It is possible. That's how the Admin Shields mod works, for instance.
Why would you even want to do that? It's just rude.
Again, this is basically what the Admin Shields mod does, it just only adds a bitmap.
I would never go to the server of anyone who had an addon like this.
Admin Shields, a lot of VIP scripts, any server with any form of eval, any server where the host knows how to use the console, so on.