When I open a file whose character encoding can't be determined, maybe it can be assumed to be UTF-8 and display whatever can be. I have tried to open some self-extracting installer shell-scripts to alter them a bit to my needs and Geany doesn't open them saying the character encoding can't be determined.
Notepad++, for example, opens such files assuming UTF-8 encoding and displays unknown characters as "NUL". I find this feature very useful.