Tried to posting a site. what do you mean by this?
Did you uploaded a site to your public_html
then it will showup automatically. Make the main file as index.html or index.php according to your language what ever you are using.
Did you tried to create hosting again means re register for hosting account. Then also if you get this error then we will inform to staff.
Just confirm it.
This doesn't voilate the rules as the can post only text and it will be updated on page. Just like a commenting. So it is not a problem until it is not taking heavy resources.
you have to ensure that they don't spam it. like posting warez links etc... because it doesn't require the login as...
You can develop your own plugins if you want in wordpress. You can even use it as CMS users and you can integrate with forums. A lot can be done with the worpress.