Markup & Pings
HTML should work in pretty much all areas of the site you can post on.
You can ping or mention a user by using @username. If they have not blocked you and are not in quiet mode, they will be notified of the ping. This only applies to threads, posts, comments and bulletins. Users will not be re-pinged if the post is edited.
Adding a user to your authorization list allows them to view your protected characters and bulletins. You can also set custom image visibility options for authorized users; for example, allowing authorized users to view your un-watermarked images, whereas public users cannot.
Blocked users cannot contact you for any reason, including messaging you, commenting on your profile or any of your characters or bulletins, requesting links to any of your characters, pinging you, or authorizing or subscribing to you. I'm thinking of blocking stuff like favorites and also inbox notifications from blocked users but I'm not sure just yet scratches head...
Blocked users will automatically be unsubscribed from your account.
For the record, blocked users will receive the exact same message they would get from a user in quiet mode ("This user is not accepting notifications."), so it won't be immediately obvious that you've blocked them unless they investigate.
Quiet mode blocks everyone on the site aside from users on your authorization list... Yeah... Note that - as with blocked users - your gallery will still be visible, this just stops people from contacting you or sending you requests.