O SciTE v2.23 no Windows parece funcionar bem com esses conjuntos de caracteres para mim. Você definiu a codificação para UTF-8?
File -> Encoding -> UTF-8
Adicional:
De acordo com a seção documentação do SciTE sobre Codificação:
SciTE will automatically detect the encoding scheme used for Unicode files
that start with a Byte Order Mark (BOM). The UTF-8 and UTF-16 encodings are
recognised including both Little Endian and Big Endian variants of UTF-16.
UTF-8 files will also be recognised when they contain a coding cookie on one
of the first two lines. A coding cookie looks similar to "coding: utf-8"
("coding" followed by ':' or '=', optional whitespace, optional quote,
"utf-8") and is normally contained in a comment.