Posting to Facebook requires a Facebook account.  Visitors can also post comments to the page using other media by selecting the Comment Using button and choosing another platform for posting a comment.

If you have a Facebook account but are not signed in, selecting Facebook from the Comment Using drop-down will open a window prompting the visitor to log in.  Once they do the window disappears and they will be able to post a comment from their Facebook account.

There is a checkbox that, when checked, will post that comment to the poster's wall as well.  If they do not select this option, the comment will only be posted to the event.