The most commonly held argument is that of Promissory Estoppel, which, in massively reductive terms, says a promise can be legally binding, even if there was originally no legal declaration or intent
Take Evendo, Waking Haven and Glimmer Seeker, and you get a decent engine for glimmers, ramp and card draw
Once you know what each card type does, building your first deck becomes way less intimidating and way more fun
Can the opponent claim they don't feel complimented by your compliment and force you to return a creature to your hand
Although it looks fantastic, it isn't as valuable as the Evolving Skies Alternate Secret Rare.
By sending one of their cards back, you force them to discard the only one left, which is guaranteed to be their strongest or most valuable card