TYPO3 Core

If you copy&paste TypoScript code into a new template, some errors appears.
Try the following to reproduce it:

Create a new TypoScript Extension-Template and open the Setup-Field for the first time.
Then copy & paste any TypoScript-Code into it. It wont work.
Press Enter. Then paste again. Only the first Line of the Clipboard is inserted an there is a mystery with Linenumbers (see Screen 1). There are blank lines and the lines are vertically misplaced.

Try to delete the Code. It is not possible to delete the empty Line 1.
Paste again: Now it works, but the Linenumbers are broken again (see Sceen 2).

Tested in TYPO3 6.1.5 and Firefox 24 and 25.

In Chrome 30 copy&paste works, but the Linenumbers are also broken (see Screnn 3).

The Problem is also well-known in all other TYPO3 Versions.