The forums have a quirk that may lead to posts being omnommed instead of posted.
When you hit "Submit" the post usually goes through. UNLESS someone has posted something in the same thread while you were composing YOUR post. At which point, your post will not submit. Rather you will get a screen that informs you that someone else has posted while you were composing and, given that, do you want to submit your post as-is or edit it.
So, once you post, make sure it is posted. And if you get the "are you sure" screen, make sure to click YES, I SRS WANT TO SUBMIT THIS DAMN COMMENT. (not actual button text)