If that's not an option, what eZ version do you run??
In 3.8 you can just download the news package or something.
In the other versions I would recommend rebuilding the classes (article and comment)
Then rebuild the user rolls that enables user to comment. Then u need to assign the right templates to those new classes.
But first, remove admin rights to the one that did this, and check the recycle bin for the missing files.
