> For example, constant time subscripting, or improved length calculations, are made possible by encodings other than utf-8. Assuming you mean different encodi

> For example, constant time subscripting, or improved length calculations, are made possible by encodings other than utf-8. Assuming you mean different encoding forms of Unicode (rather than entirely different and far less comprehensive character sets, such as ASCII or Latin-1), there are very few use cases where "subscripting" or "length calculations" would benefit significantly from using a different encoding form, because it is rare that individual Unicode code points are the most appropriate units to work with. (If you're happy to sacrifice support for most of the world's writing systems in favour of raw performance for a limited subset of scripts and text operations, that's different.)