Corporations are making these emoji and people are using them to communicate. The meanings are ambiguous, never taught in school, tied to profit motives of domestic or foreign corporations, and liable to change at a moment's notice without all parties receiving the same change. It's a mess for future of society and communication, and that it's showing up in court cases with confusion already is a leading indicator that the problems will get worse.
In general most legal writing and procedure is overwrought and obscurantist, not least to serve as a moat between the profession and the public. While I enjoy reading complex arguments and legal witticisms, such archaisms really do a disservice to the public. Many legal documents could be 2/3 the length and far more accessible without any sacrifice of accuracy or depth.
If the visual of the emoji is relevant, the defense can always fix it by showing it to the jury.
And yes, what to show for the emoji? Which platform's rendering? What about reactions to the message that can be added in some apps?
All in all I weigh emojis very little compared to other possible evidence considering how convoluted this all is.
And of course sending someone a knife emoji is not a threat. A threat requires specifics.