Very astute observations placed here on the topic of katars, and as has been noted, some key qualifying factors toward classification. As Marius said, the bejeweled examples would seem to be reserved for illustrious wear during events where persons of high standing, up to and including royal figures.
As with most forms of weapon, the functional, less decorated examples would certainly have been used in the field, or on campaign. The 'court' classification would be a presumed category in most cases, unless the weapon has specified provenance, as has been noted.
As Jose has also well noted, later decoration which included that of gold koftgari, was often applied later. These circumstances could have been brought about for numerous reasons, some certainly for valid glorification of a favored weapon with important heritage, while others of course more marketable embellishment.
Jens, your study and collecting of katars, as far as I have ever known, surpasses any other such specialized work in the arms and armour community. It would be outstanding to see your examples here with your observations!!!
Please bring them on!!!