I would be terrified about an irc chat.
Magic Sessions is still something that you would need to know to look for. An irc room, even on a moderately popular server, would be way too open. So, while seven people are cheerfully but passionately sharing diverse ideas for performing any common sleight, there would be no telling who would show up, when, or to what purpose.
I love irc. I'm about to log back into my favorite channel. I just think it would be severely disrespectful to use for a chat room about magic. Other resources exist and they can be considerably more discreet.