As I understand from conversations with mods that this is just a bug. I'm guessing a webmaster was fiddling around with ideas and set this up, but it either wasn't supposed to be implemented or they forgot to tell the mods or set up a way for the mods to be alerted to these flags.
I've been told by a high ranking mod to "do everything in your power to bypass this bug."
Here's how everyone can bypass it:
1. Copy your post before submitting. This is also important since the auto-logout bug is still active.
2. Submit the post.
3. If the moderator approval bug happens, then repost, but this time post something very simple, such as a single letter.
4. Submit the new simple post. It should go through without the mod approval bug.
5. Now, edit the simple post and paste your original post in place of the single letter.
6. Resubmit your original post. It should go through without a problem.