The move itself wasn't banned. The method of extending it was. It was banned because it would radically change the meta game if exploited to make it so Meta Knight would be the only viable competitor. It could be used to stall, and it was an unbeatable approach. Worst of all its impossible to monitor without resorting to judgment calls. I have been over this many times.
However the league was dying long before that. It suffered from lack of interest to start, then people just stopped coming around to it and the ones that were interested in it found AllisBrawl instead. We also kind of sucked at updating it... but bleh, theres better places and ways for that sort of thing.
My Creations in Modnation Racers! Check zhem!
http://community.modnation.com/en-us/players/IvoYaridovich/creations
