When communicating with other users using the Messaging system, formatting doesn't work. Granted, there is no WYSIWYG included in the messaging system, but I wouldn't have guessed that meant there is no support for Wiki-style URLs, for instance (i.e. - [[http://example.com|example]], which allows a URL using the double-bracket syntax).
Also there is no ability to edit a message, which would normally be fine, until I make the mistake of using the Wiki-formatting in a submitted message.
There's no ability to preview either. Fun!