No further response from issue author.

Please try to add a line

# -*- coding: utf-8 -*-

as the first line of your source file. I would like to see, if the character encoding is 
set correctly. All text drawing is done by the QScintilla editor widget. However, it might 
be initialized incorrectly, although I never saw such an issue on any of my systems 
(Windows 7 and 10, various Linux and macOS).

In which version did it work? What was updated since then?

When starting eric6 in root user if it works correctly, I have also tried to reinstall QScintilla, but it does not work.

Change the monospaced font and the problem persists. In previous versions this solution worked but in 20.1 no

The screenshot indicates that you have a non-monospaced font configured. Try to change this 
and let me know. If the characters are still wrong, this is a QScintilla issue. In that 
case you should report it to the QScintilla mailing list because such an issue would be 
outside my area of influence.

When I update the eric6 software, the code editor fails the text strings, showing the characters wrong.