I've noticed this from time to time, but here's an example. In the TSS forum, in the "TSA Let's Minor...." thread today, the OP bigboy61 has two consecutive posts that are about number 20 in the thread. Thi first one has the expected "original poster" indication in blue under the username to the left of the post, but the second one does not.

ADDED: I just returned to that thread and now the OP flag is showing where it should. I was apparently viewing the posts very shortly after they were made. Is there a slight lag before the OP indication appears to the left of posts? I had always assumed that the OP indication automatically appears when the post is made and isn't something that FT adds slightly later.