2018-12-07 : A creature with 0 power can attack, as long as it doesn’t also have defender.

2018-12-07 : If a creature is attacking a planeswalker, and that planeswalker leaves the battlefield, that attacking creature can still be blocked. If it’s unblocked, the attacking creature is still attacking. It simply deals no combat damage.

2018-12-07 : If the attacking creature leaves the battlefield before Raid Bombardment’s triggered ability resolves, Raid Bombardment deals 1 damage to the player or planeswalker that creature was attacking before it left the battlefield.

2018-12-07 : If you attack with multiple creatures with power 2 or less, Raid Bombardment’s ability triggers for each of them separately.

2018-12-07 : The power of the attacking creature is checked only when the ability triggers. Once it triggers, Raid Bombardment will deal 1 damage to the appropriate player or planeswalker even if the creature’s power changes before the ability resolves.