Edit: It turns out you can catch your own removing event through a LocalScript and listen for chat commands, even after the script is destroyed. +1 to HexC3D for the effort.
This is more of a hypothetical question, but is it possible for the server to receive input from a user whose player object has been removed, but still exists as a NetworkReplicator connected to the NetworkServer? My intention is to create a way for my moderators to join a server and monitor chat without anybody knowing they exist. Can this be done?
It's not possible , you can't remove the Player object, because they will lose connection to the game. Though if you create a custom Leader board it's all possible.I've just tested what happens when you remove a player's object , yet again they unfortunately lose connection.
You can make a custom leader board so that every time such and such person joins there name is not shown in the custom leader board.
~ Happy Scripting HexC3D