Utter Insignificance

• WOTC Official Reminder Textofficial rules
  Flash — You may cast this spell any time you could cast an instant.

• WWizards of the Coast2024-06-07
  Official Ruling
  If the enchanted creature gains an ability after Utter Insignificance becomes attached to it, it will keep that ability.
• WWizards of the Coast2024-06-07
  Official Ruling
  Utter Insignificance overwrites all previous effects that set the creature's base power and toughness to specific values. Any power- or toughness-setting effects that start to apply afterward will overwrite this effect.
• WWizards of the Coast2024-06-07
  Official Ruling
  Effects that modify the creature's power and/or toughness, such as the effect of Wing It, will apply to the creature no matter when they started to take effect. The same is true for counters that change its power and/or toughness and effects that switch its power and toughness.
• WWizards of the Coast2024-06-07
  Official Ruling
  Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to a creature may become lethal if Utter Insignificance becomes attached to it during that turn.

Rulings via Scryfall