I'd actually not write what they did, just that they were very helpful. It's against policy to "short-check" bags with layovers < (I think) 12 hours. It's not what you were doing, but some can do it to game the hidden city ticket aspect. I've been told in the past that agents are audited and can/will get reprimanded for violating procedure and short-checking (or checking through on 2 separate itineraries). To be safe, just send a compliment in through AA but don't give any specifics.