Only when you edit a post (changing what you have originally posted) and then edit the post a second time, the changes that you made during the first edit DISAPPEAR. It's a software glitch that probably not be resolved (I never checked with the Webmaster).
When you edit a post the second time and repost it, you have to re-read your post and make sure it says everything you want it to (and then a RE-EDIT might be necessary again).