Player Conduct Question

[Philo]

I was in a $20 NL ring game, and I hit four jacks on the river with a loaded board (Q-K-J-J-A). I was against one opponent and I bet. My opponent, who had bet out on the turn, thought for a while, and then a (good) player not in the hand said to my opponent "He has the jacks," and then my opponent folded.

I was really pissed. My question is, is this conduct within the rules or allowable?