i think that falls under number 2 of the Codes of Conduct that i'm sure everyone has read three forum sites ago.... ..right?
only yours involve spilling spoilers *try saying that three times fast*
2. A little comment while people are watching anime is only okay if the comment is made in a low voice. If you say something loud enough for everyone it should be short and to the point. If all the talking gets out of hand, it's all up to the provider of the meeting place. If he/she decides to contribute to the noise level, and it is disruptive to viewing, then someone else should take it upon himself or herself to bring the noise level down. Or ask for at least a pause of the anime so nothing will be missed. If the location provider says to stop talking in a disruptive manner, you will do so. If you do not stop when told to do so, you will be reprimanded.