1. Not currently but a new comment system is planned as indicated on the road map.
2. Comments can be posted by anonymous users and authenticated users, but unless the user is in a trusted role you should not allow users to upload images or link to external images,it poses security risks. Same issue in the forums, ordinary users cannot post images, only admins or content admins can.
3. You changed what? View roles? Edit Roles? Please explain in terms of exactly what you did, what you expected to happen, what actually happens.
Hope it helps,