True. And interestingly, the term "emoticon" was used both for the basic "ASCII" and fancy graphical representation. And while some "ASCII" sequences were present on multiple platforms, the meaning quite unsurprisingly often diverged, just like you implied. See some:
[MSN emoticons] vs [Yahoo emoticons]
:-* "Secret telling" vs "kiss"
8-| "Nerd" vs "rolling eyes"
:| "Disappointed" vs "straight face"