yes and no.

there is a package floating around in one of the evil repositories that will theoretically enable IRC through RTCOM (the way it already worked in maemo 4).

unfortunately, maemo 5 doesn't support group chat - or chat rooms or whatever you call it. the user interface will only allow you to chat with one person, which simply doesn't work in an IRC chat room.

good news though:
most probably this functionality in the UI will be back in the PR 1.2 update. so try ask the same question later.