Credit: Wizards of the Coast Mizzix, Replica Rider FromTheShire: Copying spells gets spicy quickly, and there are a ton of ways to not cast from your hand between all the great impulse cards, flashback, suspend, foretell, Etali, Primal Storm, etc
THE DARK ART OF OPTIMAL RESOURCE EFFICIENCY The fundamental logic for building around discard effects is similar to that of sacrifice you take something normally considered a drawback by the designers and then try to flip into either a neutral or even positive exchange
Then in 2017 one more ruling was added to address replacement effects: "Replacement effects that modify creatures of a certain type as they enter the battlefield will apply (or not apply) after you apply this effect
The high had a relevancy, especially since prices werent so quick to change over the course of a single night or weekend
Rules and accepted cards can vary depending on the event itself, especially on a smaller scale, but usually, miscut cards are a no-go