This is normal behavior for wp-cache, and doesn’t imply that more than one URL is in play for the same page.
When a visitor leaves a comment in WordPress, they are given a cookie so that upon a revisit their personal info can be pre-populated into the comments form.
Wp-cache keeps a different version of each page for each unique cookie that comes in (since in the case of a page with pre-populated data in the form the page _is_ different). Wp-cache does this for all pages, regardless of whether there is a form on it or not.
When you log into your admin panel, you get a cookie. You will notice that if you visit a page when you are logged in and again when you are not, you’ll get 2 copies cached by wp-cache.