Read the topic. Ghosting is totally client-side. It is the bricks being created on the client. The only way for the server to detect the player has finished ghosting is if the client tells them. The person could disable that and therefore be invisible forever. We explained they can be an obstruction in that case. Just spawn them in the battlefield, in a spawn room, and then they can leave the room through a one way teleporting doorway when they're done. Just like TomTom's server.
You completely misunderstand. It seems to be quite popular.
What I meant in my suggestion was that ghosting would make the player invincible and unable to fight at the same time, meaning that they couldn't do any harm. You might even make it so that they couldn't move while ghosting. If ghosting controls multiple things, it isn't possible to selectively ghost, unless by a really stupid script, and then you could avoid that by making part of the script ban players for ghosting control spam. However, creating a spawn room is a good bit more convenient most of the time, it's just that with spawn rooms, certain issues can arise.