Hi @SAMY
I will answer what I can and will add more info here if I can find it
I'm not aware of a way to add only comments with no questions to an evaluation form. The evaluation form is meant to be a questionnaire. To accomplish that you might consider using process automation triggers in conjuction with an email campaign to send an email to a customer after an interaction wraps up.
Some of the permissions for Quality evaluations include:
quality > evaluation > add
quality > evaluation > edit
quality > evaluation > delete
quality > evaluation > edit agent sign-off
quality > evaluation > edit score
quality > evaluation > participate
So you could restrict a role in these areas by not including these permissions