Add to that that, depending on the emoji font, the emoji will look
completely different[0]. So as the sender you have no guarantee that the recipient of your message will actually interpret your emoji as you intended. It really is beyond me why the Unicode consortium thought that putting emojis in a character set would be a good idea.
Sure, having a code point in your character set that represents a bird[1] makes sense but I really hate that font designers now have control over the way I get to express my emotions and how others perceive them.
[0]: Sure, ":)" and ":/" also depend on the font but much less.
[1]: https://news.ycombinator.com/item?id=26164409