When attempting to retexture emojis, some of them turn into a weird choppy mess. Multi-unicode characters also turn into a choppy mess such as the face in clouds emoji and even the standard red heart does not work. See attachments
😶🌫️ <- breaks entirely
❤️🩷🧡💛💚💙🩵💜🤎🖤🩶🤍 <- every single one works except for the red heart. The unicode website states that its only one character, but that doesn't seem to be the case
I think this effectively duplicates MC-262169 as Minecraft doesn't currently support ZWJ emojis
(Unrelated, I'd recommend not putting custom assets in the minecraft namespace of your pack)