I would like allow users to edit the contents of a block but prevent them from editing the block description which I only want site admins to be able to edit.
Give user permission to edit a block content type. They are able to edit the block description.
Add a permission per block content type to "edit %type description"
If the user does not have permission, the description should be displayed as markup text instead of a textfield to give some context to what they are editing.
Closed: works as designed
1.0
Code
This request is outside the scope of this project. The Field Permissions → module might give you the field level permissions you want.