ok K_brown I will bite ,
answer to your question #2 Why should there be a rule against it ? : first and foremost in most tournaments whether it be chess or sports or whatever, different levels of competency are determined by various methods and the players are then usually seperated into different levels. This is done to promote competition and fair play. If a player sneaks into a level that is much lower than his or her true playing ability don't you think that would give him or her an unfair advantage and ruin the competition ? It seems pretty clear to me and to most reasonable people. Thats why there are different levels or classes of play in almost every sport or game.
As for your question #3 : How would the rule be implemented in a sensible manner ? .... That seems pretty obvious as well. When a player is found to be clearly intentionally losing games in order to enter a tournament at a much lower level than his or her "normal" ability, then they should be immediately disqualified from the tournament and or banned from Chess.com. There are many moderators on this site that do take action when cheating is found out and the cheaters are banned. Thats the way it should be, cheating or sandbagging ruins the game and shows a severe lack of integrity.
Hello? What are we saying here? Don't the comments say be revelant, helpful, and NICE