There are situations where parts of a file will be automatically generated by an external tool and this code should not be modified at all, since the amount of code that is generated can be quite large it is possible that this gets done by accident. Therefore being able to mark an area as not being editable in the code would be a good way to deal with this.

In Netbeans for example they utilize a form of a comment which surrounds the relevant code, so for example we could allow:

// NOT_EDITABLE
....

// END_NOT_EDITABLE

to inform Qt Creator that it should be marked as read-only.