This string is interesting, they forgot to give it positioning bytes, this problem also affects the Japanese version. If you give the string positioning bytes you'll get the following when you enter the sell menu:

If you want to enable the string go to headered offset 0xDDBC and enter $54 $00, this will overwrite the first two characters of the string but luckily the unused EXPEND comes right after this so just retype the string, being sure to end it with $00.
The EXPEND text might be a similar situation but I have no idea where it's supposed to appear on the screen.