I'm back from the dead (after 5 months)!
Combine markoff chains with string manipulation and voila, you've got a bot to chat with.
Several IRC bots like rbot and
SupybotLimnoria already have this, but for the sake of finding it out myself how this works, I've done one myself.
With this one you can even (or rather only) have a private conversation!
(Read the text in the image from bottom to top … I should really change that to show the latest messages at the bottom … And add some timestamps)