Add a separator to the top of revision log

Hello,
URL: http://yourtechadvisors.com/forums/topic/test-topic/
On this page, there are revision logs showing when people edited posts. What I would like to do is add a 2px border above the first revision log entry. I tried doing this myself, but could only manage putting a border over all of them when I just need the first one. Please see screenshot.
Please let me know if this will be doable or not.

Thanks, support access is open.