TYPO3 Core

It is an absolute No-Go to use different compatibility settings in differen involved source files. Changing compatibility view while browsing pages inevitably causes problems.
As a matter of fact: don´t play with compatibility view! Ignore this feature in IE... dont´t even install it! For debugging, play with the source code... or while play with the browser settings under the security tab in IE´s internet options. No matter if its HTML or JavaScript. My opinion results from years of experience in the area of second level client support. Please hear me... I never realyy solved an issue when playing with IE compatibility view, I only made things worse.

My real problem:

I am having trouble with some functionality in the backend. But these problemes do not necessarily have to do with this setting, but you shoul definitle get the following straight:

\typo3\template.php'
line
200: * Whether to use the X-UA-Compatible meta tag
674: * Defines whether to use the X-UA-Compatible meta tag.
1288: * Returns X-UA-Compatible meta tag
1291: * @return string <meta http-equiv="X-UA-Compatible" content="???" />
1294: return '<meta http-equiv="X-UA-Compatible" content="' . $content . '" />';

Fundstellen: 'X-UA-Compatible' 5 Einträge.
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Suche nach 'X-UA-Compatible' in '\typo3\contrib\codemirror\js\codemirror.js' :
line
105: html.push("<meta http-equiv=\"X-UA-Compatible\" content=\"IE=EmulateIE7\"/>");
Fundstellen: 'X-UA-Compatible' 1 Einträge.

Suche abgeschlossen. Fundstellen: 'X-UA-Compatible' 6 Einträge. (2 Datei[en])

Only possibly the 'X-UA-Compatible' is the reason, OH and PLEASE * PLEASE PLEASE ** tell me:

How can I globally set the Value for useCompatibilityTag to False? For debugging purposes I set $useCompatibilityTag in template.php.