Сабж. Текстовый однобайтный редактор GNU moe (My Own Editor) вот уже 12 лет пилит Antonio Diaz Diaz (http://savannah.gnu.org/users/antonio).
Из коробки текстовый редактор заточен под ISO-8859-15. Свой выбор автор обосновывает так:
Moe uses ISO-8859-15 instead of UTF-8 because an 8-bit character set (combined with romanization if needed) can convey meaning safely and more efficiently than UTF-8 can. UTF-8 is a great tool for tasks like writing books of mathematics or mixing Greek with Chinese in the same document. But for many other everyday computing and communication tasks, an 8-bit code like ISO-8859-15 is much more practical, efficient and reliable. There is no such thing as an "invalid" or "out of range" ISO-8859-15 character. UTF-8 is fine for non-parsable, non-searchable documents that must look "pretty", but not so fine for things like configuration files or C++ source code. UTF-8 greatly hinders parsability (and may even become a security risk) by providing multiple similar-looking variations of basic alphabetic, punctuation, and quoting characters. UTF-8 also makes search difficult and unreliable. For example, searching for a word like "file" in an UTF-8 document may fail if the document uses the compound character 'fi' instead of the string "fi".
В новой версии:
Changes in version 1.9: Moe now loads recursively all the regular files in each directory passed in the command line. This feature makes it easier to edit a whole tree containing thousands of files. The new help key 'C-a' has been added because 'F1' is intercepted by some terminal emulators, and 'C-h' is interpreted as backspace by others. The UTF-8 decoder now converts some more characters. Cursor positions (+line,column) given in the command line are now adjusted for tab characters. The command 'goto matching delimiter' now skips delimiters inside /**/ comments. The 'N' command ('Find next' in reverse direction) has been added to the basic less emulation. Standard input is now read just once, the first time it appears in the command line. 'Remove duplicate lines' is now a 20% faster. Long file names are now cut to fit in messages like this: "File '...end_of_long_file_name' saved". An 8-bit "C" locale is now used in Cygwin so that ncurses can show characters higher than 127. A configure warning happening on some shells when testing for g++ has been fixed.
Патч для любой однобайтной локали, включая KOI8-R: http://saahriktu.org/downloads/patches/moe-1.9_any8bit.patch.lzma
Скриншот после применения патча: http://saahriktu.org/tmp/scr1498513368.png