#starscout also sounds like a surname someone from Tatooine might have

[airyairyaucontraire]

Incidentally, when and why did pony culture change to the extent that seemingly all individuals have given names and family names, eg Sunny Starscout, Izzy Moonbow?

Starscout or Moonbow would make sense as individual pony names of the classical period, as would Sunny, but Izzy (which is usually short for Isabel or one of its variants) stands out as unusual.

Earth ponies did have a tradition of family names but it wasn’t standardised - the Apple family all had apple-themed names, many of which contained the word apple, but not all (eg Big Macintosh, Braeburn), while the Pie family (who seemed to be outside the mainstream of society) had a surname and human-ish given names such as Pinkamena and Maude. There was the Cake family too, also Earth ponies, but they had given names like Carrot and Pumpkin. Mrs Cake appears to have changed her whole name upon marriage, going from Chiffon Swirl to Cup Cake, despite the fact Chiffon Cake would be a perfectly cromulent name and fit the family pattern.

Another curious thing, given the schism that apparently took place between Earth ponies, pegasi and unicorns at some point, is that ponies of all three tribes appear to have similar name structures in the “new generation” period rather than having gone separate ways.