When I want to enter the char 'ę' (right alt+e) editor insert additional '€' so in the end it look like '€ę'. The same situation is with 'ć'. After pressing alt+c it give me '©ć'.
I checked the CommandExecuting event and InsertText command is invoked twice.
That's the main problem.
The following combinations also should not insert any character (at all): alt+r: ®, alt+t: ™, alt+u: €
I am using keyboard polish (programmers) and polish language in Windows 10.