Here's a related bug I spent last night fixing:
I've been encountering an issue off-and-on over the past few years that seems related.
Sometimes after I make a post, my own post will show up in the Unread Topics thread. Even if I click on it again and refresh the page, it can still take several attempts (or several minutes) before it will finally mark as read. I'm not sure if the number of attempts makes a difference. To me it seems more related to time. That is, if I try to get it to mark as read right away, it can take several attempts before it will finally be marked as read. But if I ignore it and come back to it later when I would normally check for unread posts, it will be marked as read on my first attempt.
I only started having this problem when I started using the HTTPS version of the website. And back when using HTTPS here on the forums was still new and optional, the problem almost always went away when I stopped using HTTPS here on DC.Here's a thread about it.
So hopefully your fix will fix that issue, too. I'll try to pay attention to whether or not it happens to me again in the near future.