Avoiding a segue into quasiquotes here.  The idea of inferring backticks in the generated AST is not something I've completely thought through!

The enhanced proposal is a **breaking change**  It turns *all* backticks into interpolated identifiers.  To output a literal backtick it would need to be doubled.

The basic proposal breaks nothing.  It merely enables a syntax that can only ever be an error under the current implementation of string interpolation.