@Dodo: Yes, we replaced them on the server ... the way the code works in that we convert your text smiley into a <img> tag pointing at that location... we keep that converted html in the DB and only regenerate if you edit. So, changing the URL in our code would have fixed all new smileys (and it did), but changing the source images means that any old reference to the smiley in a comment or perhaps copied from within a comment will also be updated.