Steps to reproduce:
1. Create a site template and don't allow modifications to it
2. Create a site with the site template
3. With a site administrator try to delete or move a page "inherited" from the site template from the horizontal navigation or the manage pages tree
Right now the horizontal navigation allows both moving and deleting. For this it would be enough to just prevent those operations for the entire navigation.
The manage pages tree allows moving the pages. It should prevent this for the inherited pages and show it clearly through a different icon or something similar