Yeah, in my head canon there are a few rank peculiarities:
- General promotions, granted only by promotion boards following recommendations, time in service, and passing necessary exams (i.e. Bridge Officers' Test for most Commanders). Signed by an Admiral and, for flag ranks and captaincies, approved by the Federation President and/or C-in-C. We see Worf and Sisko promoted via this method, as most other promotions happen between seasons/episodes.
- Field Promotion, granted by an Admiral, or even Captain in exceptional circumstances when a billet needs filled without being able to go through the full channels. Given to an officer who otherwise fills all or most of the qualifications. Temporary field promotions (or demotions) are when there is an expectation for the decision to be reversed in short order. "Permanent" field promotions are when there is an expectation that the promotion will be approved in time. Field promotions are entitled by law to wear the rank insignia of the rank they are promoted to. We see field promotions given to Riker (temporary), Paris (likely permanent), and Tuvok (permanent).
-Provisional ranks, given by Captains or COs to otherwise unqualified personnel in order to fill billets when no one else is available. Have their own seperate insignia to denote the provisional status. Rarely used except in cases of long-term missions outside of communications range. We see this in Voyager, of course.
The field promotions seen in The Valiant were simple wargame notations, and may have been done illegally by Captain Watters, depending on if a Field Promoted Captain can field promote others.
