@tygb: The article you link to does not relate.
@tengda: is referring to the ability to rename files from the window title. This ability in some apps such as Pages and Preview is indicated by a "DOWN ARROWHEAD" symbol to the right of the window title (Unicode U+2304).
In these apps you are suppose to be able to click on the window title to change the document's title and to even move it to a different folder. But the behavior changed with Mac OS Sierra.
Previously, you can simply click on the name, change the name, and press RETURN for the changes to be saved.
Now if you do that, it does not.
I found that you have to go to the extra step of pressing TAB then RETURN to change the document's title from the app window title. So I think this is a bug introduced in Mac OS Sierra that decreases the user experience.
Other Apps like PDFpenPro still have the old and correct behavior of pressing RETURN to save changes to the document's title in the window title.