What lore do you ignore?

[Anonymoose]

Do we have any other examples of interracial relationships being taboo, other than Hilda, who is about class and situation as much as actual race?

Examples are difficult to come by. This is something we've been told more than shown. The Sixth Astral Era featured a lot of racial animosity given the times and places and means of different populations showing back up to the continent. This was to the point of races concentrating in different cities, and then those cities also have periodic historical bad blood themselves. Cultural animosity and racial animosity are entwined, in many cases. But if you peruse any compilation of quotes about interracial relationships and mixed-race children and you'll find a lot of, "such relationships are possible, but are fairly rare for cultural reasons". In the age of adventurers, such attitudes are increasingly less common.

Do we actually have any evidence that people generally refer to the world as Hydaelyn?

The 2010 lore was that the planet was named Hydaelyn but not many people used it because, to think to do that, you'd need to know what a planet was - and that you were on one - and that there were (or at least could be) other ones out there. If you were ignorant of all that, you'd never bother to learn (or at least rarely think to use) the word for the distinction. NPCs saying "on Hydaelyn" are rare, and most often are well-educated. Godbert, Cid, Jannequinard, Mikoto. The most unlikely one is Medrod, the miner out in the Shroud during early ARR, who says "Nothing on Hydaelyn is worse than what I saw..."