He's giving his post a more recent "last post" status. It's so that it's displayed near the top where people are likely to look. In other words: a "bump" up.
He could do the same thing by editing the original post in some way. I just tested it by adding this paragraph, but all you would need is a single character (or possibly no change at all, just a re-submit).
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 Black 03 PT Turbo & Black 94 Impala SS
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