If you are being monitored by FB, they can edit and even remove your post before you get to submit it.
I was in the process of commenting about the violation of flag regulation regarding the US flag by police departments. As a result, about halfway through my post, it stopped accepting text, then deleted it while blocking me from commenting.
To try to verify the process, I went to another post and commented with no problem. Then back to a public agency (Another police department), and watched my post vanish again.
Proactive big brother feature is here. How much longer before FB swats you while posting?