I suppose you could consider IRC and IM to have some significant feature overlap, but I'd still regard them as essentially different things. IRC's core feature

I suppose you could consider IRC and IM to have some significant feature overlap, but I'd still regard them as essentially different things. IRC's core feature is larger-scale many-to-many conversations, and IM's core feature is one-to-one conversation, and this in turn leads to significant differences usage patterns, interface conventions, network protocols etc. that even further differentiate them.