That's a good point about the edges.
I think one of my concerns here is there is a lot of meaning tied up in faces, and the meaning is not always quite universal. If you change the emote graphics, it can change the underlying meaning the original author tried in convey. Even subtle changes can have a big difference in interpretation.
Another point that is getting to me just now, is those animated emotes above the post textbox are quite distracting while I'm writing.
(That's right, shake that fist!)
Edit: Oh geeze, they mess with line height too.