Whirling Dervish

• WOTC Official Reminder Textofficial rules
  Protection — This permanent can't be damaged, enchanted, equipped, blocked, or targeted by [quality].

• WWizards of the Coast2021-03-19
  Official Ruling
  If Dunerider Outlaw dealt damage to an opponent who later left the game before that turn's end step, its ability still gives it a +1/+1 counter.
• WWizards of the Coast2021-03-19
  Official Ruling
  Whirling Dervish's triggered ability gives it at most one +1/+1 counter each turn, regardless of how many opponents were dealt damage beyond the first.
• WWizards of the Coast2021-03-19
  Official Ruling
  Whirling Dervish's triggered ability checks to see if it dealt damage during the turn to an opponent of its current controller. If it dealt damage to player A, then player A takes control of it, the ability doesn't trigger.

Rulings via Scryfall