For me, the vivaldi devs have done a more fundamental mistake than the csd: they made an electron based app. As far as I am concerned, it is my choise to not use any electron-based bs.
Also, the screenshots on the other thread you mention do not have any sort of csd, just a hidden title bar and they were made 8 YEARS ago, back when opera was presto based and could allow almost any change to its ui.