I don't think I've used the search function for the board before tonight - I've really got to say, it's quite nice how you have it set up. Very easy to find what you're looking for and get to the proper thread.
Is there any particular reason your current IP address is listed in the header of each message, though? I thought it was odd that someone had the same IP as I did, and then I noticed all the posts did.
I guess the difficulty comes in determining the timestamp itself. Example: Posts 1-10 happened at time A. I read the thread at time B. Someone posts #11 at time C. I mark forum reador mark to here at time D. Which time gets saved?