Yes, you are right. But he is also reddit customer, uses reddit api and legally obligated to follow terms and conditions, and they have confidentiality clause about communication there: https://www.reddit.com/wiki/api-terms/

I guess they can now sue him and request to pay damages, which likely will be large.

Also, according to random article in internet, California law requires him to ask consent too:

Generally, if both parties are within the same state, the state law will apply. When one party is in California and the other one is outside the state, the two-party consent rule applies to actors outside of California, if they are communicating with people in California who have not given consent. Essentially, California protects those in the state from being recorded without their consent even where the out-of-state actor is in a state which permits “one party consent.