Guest posting is allowed only in the Help forum. The feeling was that if you were looking for help, you might not be on your usual computer, or it may not be working properly etc. Also, we always find it a bit annoying that you have to register on sites to post a simple message.
As for Mr ffgfgfg, we have taken steps to stop any reposting. As with the old site, we won't be discussing what these actually are. But he's the only one causing a problem, so it isn't worth getting upset about.