Avoid the use of emoticons and emoji in text-based communications and never embed them in images.
In short messages that will only be seen once, a widely understood emoticon such as the smiley face might be acceptable (for example, some support content or blog posts) if the context is casual.
Emoji often convey tones that may be inappropriate in certain contexts or cultures. They’re also difficult to localize and tend to diminish readability and comprehension.
If you need to refer to emoji, you should spell emoji the same in both the singular and plural noun forms.