That’s not true. Emojis are Unicode characters just like `a` or `ß`. When I type <an emoji character> on my computer it doesn’t magically change font in the middle of the sentence; it’s just a character.
Emojis are Unicode characters, and some emojis appear in all sorts of fonts, but the more fancy emojis, as well as the color renditions of emojis, appear only in the system color emoji font. The font is changed in the middle of the sentence, as part of font fallback.
On my system I've manually updated the Noto Emoji font to get emoji 14 support because I'm not updating to Ubuntu 22.04 on my daily driver to get the new font support.
Emoji are often rendered using the system's font fallback mechanism. When one font doesn't have the glyph required, another font that does have the glyph gets picked. Most fonts don't have glyphs for non-western scripts; there are only a few fonts out there that cover most of the Unicode standard, often made up of several fonts combined.
You're not manually changing the font-face mid sentence, but when you use emoji the renderer is definitely switching fonts to one you didn't specify.
> it doesn’t magically change font in the middle of the sentence
It's not magic but it can happen. In fact, it usually does. Helvetica doesn't have emoji glyphs. Guess what happens if you drop an emoji in a block of text formatted with Helvetica?
