Coda had some light issues with pinyin input for a few years now. Pinyin is the phonetic input method used in Mainland China and it relies on a on-screen suggestion list of characters that the user chooses from as they type phonetically.
The issue is that when typing inside a cell, Coda would automatically select for you the first suggested character after typing only one letter.
As annoying as this is, at least before the new editor one could hit backspace to delete the selected wrong character, start over, and it would work. Now when you start over Coda stubbornly keeps auto-selecting characters.
I have had over 10 colleagues complain about this over the past few days as the update got rolled out. This bug has been raised many times before with not a line of acknowledgement from the Coda team: