How to remove the "Reply" box at the end of posts and pages

The bottom "Reply" section is a function of the "comments on/off" for each page or post in the page/post editor.

You can choose whether to have this visible or not on pages and posts.

Scroll down the editor page and you'll see two check boxes inside the "Discussion tab" that say:
Allow comments.
Allow trackbacks and pingbacks on this page.

I leave BOTH unchecked (you can check trackbacks if you want to). Unchecking "Allow Comments" removes the "Reply" box as the end of pages/posts.

If you can't find the discussion tab you need to find the "Screen Options" drop down menu at top right of the page editor and check the box that allows the "Discussion" options tab to be displayed in the editor page.