I have some screen recording software on my computer that I occasionally accidentally leave running. One time, without knowing that I was recording myself, I ended up watching a whole movie with my friends, so the whole movie and our conversations were recorded.

A couple years later I found the video file and decided to rewatch the movie via the recording I took, so I was also hearing my conversations from the past.

So many times during the movie rewatch, I would come up with the exact same response in the conversation just before or after my past recorded self would say the same thing.

I never used IRC so idk much about the clients, but is it possible his client just did that as a packaged feature?