Currently it requires custom code and workarounds to allow anonymous users to interact with a Drupal site. There is no API to handle anonymous users.
In case of the core Comment module we have to make use of ugly use-case specific implementations to allow anonymous users to post comments: There are specific properties on the comment entity that are only required by anonymous users which hold the e-mail address, name, homepage, etc.
Adds an input filter to allow case tracker in Open Atrium to link to other cases in the same style as on drupal.org issues with a shorthand token [#nid].