The blank message has been an ongoing problem with the forum's editor, limited mostly to Firefox users, since it was first implemented in the last site redesign. It's a random issue with what is essentially black box code so very hard to fix. Unfortunately, the company that sells it was never able to resolve this issue and has since stopped service updates entirely, so the only way to fix it is to rip out and replace which will happen in a coming redesign of the site. Until then, view the message immediately after posting. If the content isn't there, edit it in. I apologize for the inconvenience but that's all I can do at this time.
Sometimes people will have second thoughts and remove the content of their post, so it's difficult to tell if a blank post is accidental or purposeful. It will never be due to moderation because in that case the entire message is removed and not seen at all.
