This is definitely an example where "character" was the wrong word. We start out OK with bytes being distinct, but by the end we're talking about how a character is made out of several characters. If we think in terms of code points (Rust's native char type actually provides here a slightly different thing, a Unicode Scalar Value, which certain types of code point are not, but close enough) clearly a code point isn't made out of several code points, so we needed a different word.

I like squiggle, if you're a text rendering engine you might want to use "glyph" although you might already need that word for something else. But try to avoid character because that word already has far too many meanings, most of which won't be what you wanted.