[Scanu]

Ok then don't worry about that, seems like I better stay with the vbulletin 5 mode without addons (I've fixed css) or stay with the html mixed mode without vbulletin template syntax highlighting because I'm not skilled enough in javascript coding to fix one of these 2 problems.
I think you didn't imagine that. He said that he would have released a codemirror version but I think he never did. Nevermind thank you for your help

And for the plugins part, I guess it's impossible since there aren't many hooks there my solution is different from the nerbert's one and it's editing template.php file adding js resources at the start and adding Codemirror setup after the textarea is printed, and i Used the javascript variable textarea_id.