I don't know much about IRC chatrooms, but almost every form of messaging has the originating IP address logged somewhere. However, there are ways around this that are render it untraceable.
Plus if it is in Super Secret Sniper Code the others in the room wouldn't know what's going on. Hell you could just ROT13 the messages and people wouldn't look twice at it.
ROT-13 is pretty recognizable if you see enough of it. The high frequency of certain letters and words in English stick out after ROT-13. (think "...e...", "a", "and", "the").
One of my favorite .sig's is "For security, this message was encrypted with two rounds of ROT-13."