After clicking preview on a Slashdot comment, I decided I wanted to add a sentence to my post. While the preview was loading, I started typing in the comment field. However, once the preview was loaded an displayed, it did not include the addition. Since the comment field now went away, I took it for granted the edit was gone, and decided to simply publish the comment as the preview showed. However, the published comment did include the half-written sentence I had added to the edit field while the preview was loading. I suggest disabling the edit field while preview is loading.
Browser: FF 3.5.1 in Vista 64-bit
Thread line: http://science.slashdot.org/comments.pl?sid=1317769&cid=28863161