+If you mention a forum (you are a member of) in a new posting, the posting will be distributed to all members of the forum, regardless of your privacy settings for the posting.
+Also, if the forum is a public forum, your posting will be public for the all internet users.
+If your post is private you must also explicitly include the group in the post permissions (to allow the forum "contact" to see the post) **and** mention it in a tag (which redistributes the post to the forum members).
+Posting privately to a public forum, will result in your posting being displayed on the forum wall, but not on yours.
+
+Additionally it is possible to address a forum with the exclamation mark.
+In the example above this means that you can address the bicycle forum via !bicycle.
+The difference to the @ is that the post will only be sent to the addressed forum.
+This also means that you shouldn't address multiple forums in a single post in that way since it will only be distributed by one the forums.