This can be huge in white decks that rely on value from things like Chromatic Star, Thran Dynamo, or Scrap Trawler to outvalue your opponents or enable infinite combo paths
We should have been better, we can be better, and we will be better. Banning cards from competitive play is done all the time, but the removal of the cards from the database is unusual and speaks to the seriousness of the action
Generic mana is a cost that can be paid with any color, while colorless mana is a specific type of mana produced by certain lands and artifacts
If the creature this Aura would enchant is an illegal target by the time Knightly Valor tries to resolve, the Aura spell doesn't resolve
Traditionally, it's quite normal for the newest Pokmon set to lose value in the first few weeks after release, as inflated preorder prices give way once the products can be bought off the shelves