How to disable avatars in posts and comments?

How can I switch off avatars in theme settings?
Corresponding checkboxes are disabled on admin/appearance/settings/ns_theme .

I have just installed Nodestream 7.x-2.0-alpha13 and plan to use it for a small web newspaper project. Lots of small questions arise, however, in spite of having read (all) and understood (part of) documentation. I hope these can be asked here. Please direct me if there is some other place (a group perhaps?) for such.