Inserting a narrow character into the middle of an East Asian wide character:

中国 ESC [ D x:
中国x

xxx中文 ESC [ D x:
xxx中文x

Inserting a narrow character into the middle of an East Asian wide character,
in the middle of an 80-column line with mixed narrow and wide chars:

xxx[...]xxx中文xxx[...]xxx你好xESC [ 24 G y:
xxxxxxxxxxxxxxxxxxxx中文xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx你好xy

xxx[...]xxx中文。xxx[...]xxx你好ESC [ 24 G y:
xxxxxxxxxxxxxxxxxxxx中文。xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx你好y