first, sorry for destory the install page, and recovered soon
second, pls limit the priviledge of wiki, it's dangerous
Unfortunately, I don't think there's a way to stop someone from deleting a page on a GitHub wiki wtihout also restricting editing. The good news is, every GitHub wiki is its own git repository, so anyone with commit access can recover an accidentally deleted page with a simple git revert (ran into this issue when someone accidentally deleted a Diaspora wiki page about a month ago).
The wiki will be deprecated as soon as the new Jekyll site goes live. Should be pretty soon.