The non-control characters of ASCII are largely characters you might actually want to put in a document. TeX uses some of these as markup, e.g., the dollar sign to bracket maths mode and the ampersand as a column separator in tables. Typst takes this much further, using plus and minus signs to introduce list items, at signs for references, and so on.
Ideally, all visible characters should produce themselves in the printed output, except for the backslash introducing control sequences that represent all of the markup and braces for delimiting the extent of parameters to those control sequences. This would produce a very predictable and easily-parsed syntax.
The non-control characters of ASCII are largely characters you might actually want to put in a document. TeX uses some of these as markup, e.g., the dollar sign to bracket maths mode and the ampersand as a column separator in tables. Typst takes this much further, using plus and minus signs to introduce list items, at signs for references, and so on.
Ideally, all visible characters should produce themselves in the printed output, except for the backslash introducing control sequences that represent all of the markup and braces for delimiting the extent of parameters to those control sequences. This would produce a very predictable and easily-parsed syntax.