Im curious, with the Kaldorei and Sin'dorei, I dont think i have ever seen any conflict between the too races.
You would think, since they both have different cultures and ways of their life, there might be some sort of disagreement towards something.
Yes, in ancient times, they were once the same race, but you don't recall much relations to either race in WoW. It feels like WoW never really fleshed out some of the Elves lore. Kaldorei and Sin'dorei seem so much different from each other, yes given the years of evolution, but its almost if they are not the same sort of being.
The only relation I can see is the fact that the NPC Blood Elf guards are Night Elf models. But that's more in-game sort of thing.