im not sure of anyway to prevent the information from being resent but here are some suggestions:

1. drop a cookie for each visitor and then if they submit information signify that in the cookie value somehow. this way when the page is loaded it will check the cookie to see if the info that is being sent was already submitted. if it was then it ignores it and simply displays the messages otherwise it will insert the submitted information bc it wasn't submitted before then update the visitor's cookie to show that they already submitted the information

2. place a link on the page that says refresh posts (or something) this link will invoke the script to just display the posts without submitting anything

hope this helps