Any idea what these are/do?

[HouseOfHam]

While digging through the BI exe, I came across the following strings:

no_rebel_faction_set
no_default_faction_set

Any idea what these are/do?

[Squid]

Just by the names I'd say there string for use in descr_regions.txt and descr_strat.txt respectively when you don't want to set the corresponding lines to an actual rebel group or faction. What other stuff was around these strings, as sometimes that gives a hint as to the intent of them.

[HouseOfHam]

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;              Regions names generated by Romans Campaign Editor
 no_rebel_faction_set    no_default_faction_set  
     legion:     Failed to save region map   ************** STARTING CAMPAIGN EDITOR

   descr_strat.txt %s/%S/descr_strat.txt                               ; Custom campaign script generated by Romans Campaign Map Editor

campaign                          end
unlockable
   marian_reforms_activated
  marian_reforms_disabled
   rebelling_characters_active
   gladiator_uprising_disabled
   night_battles_enabled
 brigand_spawn_value     pirate_spawn_value  win_conditions
    end_win_conditions

      ;;;;;;;;;;;;;;;;

[Aradan]

Maybe default internal values, if there is no default-faction/rebel-faction set in DR? I don't see any real use for them tbh.