Hello,

The workflow emails are sent to approvers (who are assigned to that workflow step) and always to Roles (Users) with 'manage workflow' permission. This is current design and it cannot be changed in user interface. You would need source code to change it.

If I correctly understand your setup, you could remove 'manage workflow' for all the roles except one admin.

The comments can be added when the user is in a role that is allowed to approve/reject the document in current step.
Do you experience different behavior?
Or, do you want all users to be able to add comments in all workflow steps?

Regards
Zdenek