If ADOM is going to try to appeal to casual players, those mostly don't know how to install an IRC client. They don't even know what IRC is. And they don't want to read documentation to know.
I also have seen this work in ToME and I think it's a nice feature to have, as long as it can be turned off.
However, I see it as very low priority, I'd also prefer the precious development time to be spent in other issues.