Whispering Snitch

• WWizards of the Coast2018-10-05
  Official Ruling
  If you surveil before Whispering Snitch enters the battlefield, surveilling again during that turn won't cause its ability to trigger.
• WWizards of the Coast2018-10-05
  Official Ruling
  In a Two-Headed Giant game, Whispering Snitch's ability causes the opposing team to lose 2 life and you gain 1 life.
• WWizards of the Coast2024-01-12
  Official Ruling
  An ability that triggers "whenever you surveil" triggers after you're done surveilling, even if you have fewer cards in your library than the number of cards you're instructed to surveil. It even triggers if you have no cards in your library.

Rulings via Scryfall