What happens with race-rep when you racechange?

According to a topic over at the battle.net forums, blizzard indicates that they will swap your racial reputation with that of the new race. The official KB article about this has been moved though so the link is broken now, but it should still function in the same way, as it seems to be a very sensible solution from the developer's standpoint. So, for example;

A dwarf has an 'Exalted' reputation with Ironforge, and a 'Friendly' with Stormwind. After changing their race to a Human, they will now be 'Exalted' with Stormwind, and 'Friendly' with Ironforge.

Whether the developers thought to close the loophole with the Nightborne specifically I can't expound on currently, there may be an exception in place.