Does blue Ahri's Inquisitive ability target, and does it therefore trigger Deflect?

Ruling: Yes, Ahri's Inquisitive ability targets and will trigger Deflect. A target is any specific choice required by an effect.

Nuances:

• AOE effects like "deal damage to all units at a battlefield" only target the battlefield (the specific choice), not the individual units
• Effects that instruct players to decide targets upon resolution do not target
• When a triggered ability like Ahri incurs a Deflect cost, you can choose not to pay it, which prevents the ability from finalizing on the chain
• If you cannot pay the Deflect cost (e.g., no runes available), it's treated the same as choosing not to pay
• Deflect is not an "optional cost" in the rules sense - optional costs use the word "may" with "as an additional cost"