For that level of UTF-8 editing, a non-mulitbyte version of the editor suffices. In fact, you can insert and modify multibyte signatures and names using the map facility, however the glyphs are not rendered on screen but are shown at the byte-level.
Improvements are in order, and should be made, but the mere inability to visually render multibyte characters is not always a showstopper.
Or it could be just as simple as me jotting down some notes in my native language, which includes such exotic characters as ę and ą. You know, so I don't have to go back to using a code page like back in good old DOS days, that I'm actually too young to have lived through.