Not particularly. Lua doesn't do anything to make storing utf-8 in strings difficult. You have to bring your own Unicode library for doing anything nontrivial,

Not particularly. Lua doesn't do anything to make storing utf-8 in strings difficult. You have to bring your own Unicode library for doing anything nontrivial, but that's true of everything in Lua. Using ICU from Lua isn't substantially different from using it from any other lanugage.