[ssokolow]

> I didn't know that unicode changes the definition of grapheme in backwards incompatible fashion annually, so software which works by grapheme count is probably inconsistent with other software using a different version of the standard anyway.

This is EXACTLY why Rust's standard library is blind to graphemes. Support for the case where your company requires a specially certified toolchain that lags five years behind Rust upstream is an explicit goal that they address by breaking the stuff that changes quickly out into minimal crates that can be audited, updated at a quicker pace without requiring toolchain updates, and which have the option to continue to support older compiler versions indefinitely.