Oh, interesting... May I ask what "UTMJitterData" is? Your own variant on STMJitterData?
And as long as it works for you, that's good! I always keep my code exposed so people can customize it as they see fit. I suppose this way, if you're more used to editing code than using the inspector interface, you can just change values in here to edit your effects!
Emoji support unfortunately can't be included by default until Unity figures out how to render emoji in their inspector windows... but you're not using inspector windows, so this code may be useful to you: https://pastebin.com/qr9me3GA
Just follow the steps in the start of the file with how to organize your folders with the emoji textures, and this *should* work. The code is similar to what you're doing, where it will create a quad texture dynamically as an emoji is requested. You just add the script as a component to whatever object has SuperTextMesh to add this emoji functionality.
You can also just use quads directly to insert emoji or whatever other symbol without needing to convert it from an actual emoji character, first. (That might be good, because that awful, long regex string is all I could find in terms of detecting if a typed character is an actual emoji)
You may have to uncheck "remove emoji" which is under the "Beta" foldout in the SuperTextMesh inspector. This boolean is there because trying to use emoji directly with the inspector was causing so many problems, I just disabled it since STM can't render native emoji anyway.