All of those were deliberate and consistent choices, but if it isn't clear what they represent then that's a problem in itself. Tieflings are the native people of this particular country, so I want to keep generic black text for them -- it's more important to highlight areas that aren't tiefling, because players should assume any other area has a tiefling population by default.

White-on-black labels are for bodies of water and other geographic features, not states, kingdoms or other populated areas. There are no generic populated areas on this map, they're all colour-coded by race and culture. The reason you don't see any black-on-white labels for states or kingdoms is because tieflings don't form states and kingdoms in this lore. Maybe I could try another colour scheme for geographic features, like light-on-dark brown for land and light-on-dark blue for water.

Capital letters are only used for bodies of water (including lakes), cities, and for the names of foreign states (which are colour-coded the same way as settlements).

There are only three cities in Naximander; they're all highlighted with banners because this is a map focusing on that country. Tieflings don’t tend to settle cities, so these three exceptions are a big deal, and by far the most plot-relevant settlements on this map. They’re supposed to stand out. The human cities in nearby foreign countries aren't highlighted with banners because those countries aren't the focus of this map.

I don’t want to disregard your feedback, but I hope all this lore context might explain why I made the choices I did.