@pmario Here are some notes from my own testing; I have not being using any version of codemirror of late so I have a somewhat nieve perspective;
Control Panel > Settings > CodeMirror
This should be pointed to perhaps even from the editor or at least documented better. Half of what codemirror can do depends on visiting here;
“Whether or not to automatically close tags” this is the first of a number of clunky instructions. If it relys on a checkbox it need only read “automatically close tags”