Fix bug: screen rotation erases unfinished text

Problem: If you start writing a comment, and you tilt your smartphone to the side before you send it, your text will be lost and you have to start typing it again. This could be annoying if a user is forced to retype a long reply.

Cause: Reply text is not saved in the instance state. Automatic saving mechanism doesn't see the EditText field, probably because we create it dynamically.

Solution: Explicitly keep the unfinished reply text in instance state to avoid loosing it on screen rotation.