Eliding many intra-comittee process details, the C++ working group responsible for language evolution voted a paper as ready to forward to the group responsible for standardese a paper adopting UAX 31 rules for the syntax for identifiers, using XID_Start + LOW LINE and XID_Continue.

This replaces the white list of allowed code points from last millennium, and fixes some mistakes like allowing RTL modifiers in identifiers.

Current draft of the paper is available at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1949r6.html

I wanted to thank the Unicode committee for UAX 31 so that we didn't have to reinvent the wheel.