I am very happy with the latest autosave/version "aspect", TextEdit won't allow you save like whichever additional file type than .txt. Just attempt editing HTML file within TextEdit! and Hit command+s, otherwise just close the file thus it saves lone and your superb html file extension is altered to .txt. No issue what you attempt to carry out; it will for all time modify the file extension. I didnít not understand what kind of feature is this?