Created attachment 116625 [details]
Sample document with input field in protected/editable section

Input fields in protected and editable sections can not be edited with backspace or del keys. Marking parts of the content of the input field and overwriting the conent works as intended.

Steps to reproduce this Bug:

1. Create new writer document
2. Insert a input field (Insert -> Fields -> More Fields...)
3. Mark the area that contains the input field
4. Insert a section and set the section to protected: true and editable: true

The input field should be editable and all other parts of the section should be read-only. In the current 4.4.X builds you can type to the input field and it is possible to select content from the input field and overwrite the content. But it is not possible to delete content via backspace or delete keys.