In a discussion titled ‘Flair not allowed for automatic trust level groups?’, slackmoehrle reports that while new groups allow flair assignment, existing groups (named after trust levels) do not — despite being able to assign flair in group views. pfaffman clarifies that trust levels are not actual groups, even if they appear similar. slackmoehrle confirms the naming confusion and reiterates the issue: why existing groups can’t have flair while new ones can. awesomerobot explains that flair for automatic groups (like trust levels) is not currently supported because they lack features of manual groups — notably, they can’t be set as a user’s primary group, which is required for flair display. This feature has been proposed before here and may be implemented in the future, but it’s not a current priority. As a workaround, a theme component exists to add trust level flair: Trust Level Avatar Flair.