Preventing users from being to delete their own posts

I was curious if Admins can disable regular users from deleting their own posts. So for example, say Sarah posts messages on Glip. Can I make it so that Sarah can't delete any of her own messages and only Admins can delete any messages? If so, how can that be done? Also, can I make it that Sarah can't even edit any of her own posts? If so, how can that be done? And is it possible to make it so that none of the non admin people can delete or edit any of their posts...not just poor Sarah?