If you have grown up with computers and computer networks in the early days, replacing smiley character combinations with graphical icons is evil at best. I am still upset that Apple can‘t provide a hacker compatible option to turn that stuff off. Instead, when I type something like chown(8) in a chat, the number gets replaced with these nasty little things.
Today I reached my limit and went for a hunting session. And I found the little bastards. They are hidden in a property list file in the InstantMessage system framework. You can change the mapping in the files (SmileyTable.plist) manually or – to make a long story short – you can just kill them by typing:
sudo rm /System/Library/PrivateFrameworks/InstantMessage.framework/Versions/A/Resources/*.lproj/SmileyTable.plist
And the martyrdom is over.