Wait - I found that if I change the Text Viewer -> Viewer Options -> Encoding setting to UTF-8, the diacriticals get displayed properly. That's great!
Now, is there a way to turn off line wrap in Text Viewer? I can't find it, and so I still prefer Text Editor for this file and would like to be able to automatically open the file from my shortcuts menu with Text Editor rather than Text Viewer, if possible. Again, thanks.