I've tried the

Navigating multi-byte characters is "wrong" on REPL. Without telling you the actual behavior, I'd like if you try doing the following. Fix the errors in this statement- System.out.println( Seq( "允走 ) ) ).

You will notice that when you're on the Unihan characters, you'll have to do Ctrl-F/right arrow twice for the cursor to seem to move forward. However, the actual movements registered 4 such forward characters (2 times for each Unihan), so the cursor may show up right after the second Unihan character but you're actually two places forward from there. Needless to say it's a "wrong" behavior and can be annoying.

This could likely be an issue with jline, or the terminal software itself too.