Nobles receive a rating in the turn reports based on their magical abiliity:
maximum aura label ------------ ----- 6-10 conjurer 11-15 mage 16-20 wizard 21-30 sorcerer 30+ ??
For example:
Osswid the Brave [5639], wizard, with three workers
The Basic magic [2800] spell Appear common [2803] allows magicians to prevent this label from displaying.